and Air Conditioning
FAQ for 7xx/9xx/90 Cars
Vacuum Controls. [Symptom: leak sound from heater controls.] That vacuum
leak is almost certainly your floor/defrost diaphragm. It is on the left
side of case just above the accelerator. pedal. This diaphragm unit is
double acting, i.e. it has vacuum to pull it both ways, blue hose for defrost
and yellow for floor. There is a boot that seals the side that yellow hose
applies vacuum to and when this boot goes bad it leaks when you use a/c
or floor settings. It is a HARD job to replace this diaphragm unit. It
requires removing a lot of under dash parts and ducts and then standing
on your head to reach two extremely hard to get at nuts. I would try blocking
the yellow hose with an old style fuse (the glass w/ metal end cap kind)
and see if you notice any real compromise in operation, you won't ever
get the full flow to floor and you'll always have some air out of defrost
any time that you aren't on a/c.
to Heater Control: Remove the glove box and you can see in there if
the warm/cold air flap arm is moving as you move the lever. If you need
to go further, to best get access to the rear of the HVAC controls, remove
the complete ashtray assembly (as if replacing a fuse), remove the plastic
compartment above the ashtray (two screws behind the plastic cover surrounding
the cig lighter) and then PULL out the radio from the plastic box it lives
in and undo the Phillips screw at the back of the radio box and pull it
out. Then remove the plastic panel around the HVAC controls (just pull
on it, it's not that brittle), and you will expose a few Phillips screws
that hold the HVAC controls in place. Unscrew and pull out the entire mechanism,
which is pretty hard since there's hardly any slack in the wires etc.
Conditioning Vents Not Working. [Query; 86 740:] Every now and
then, when using just vent or a/c, the air stops coming out of the panels
vents. If I switch to defrost, I can feel the air, so the fan is
working. [Response:] There are 4 areas where the source vacuum
can be shut down and make your vents not change over:
1. [From Bob] Start by checking
the vacuum supply hose under the hood. Under-dash leaks are extremely rare.
The vacuum hose for the A/C-heater can be found under the intake near the
trans dipstick tube. Look for a small (1/8" diameter) white plastic hose.
It goes from firewall near heater hoses and winds its way to a tee with
a check valve conected to a larger hose, ending at the intake. It is common
for the hose to rub through from chafing on other hoses or wiring harnesses.
When you find the leak, cut the hose and splice with a small piece of rubber
2. the hose into car near accelerator
pedal under hood has no vacuum on it due to being disconnected or damaged
3. inside the car under dash that same
hose can be crushed up above and to the right of accel. pedal. Repair it
with a piece of the rigid little spray tube that comes on aerosol cans
4. behind the control head there is another
place where there is a "y" fitting in the source vacuum hose that can collapse.
Repair as in #2
5. The floor/defrost diaphragm is leaking.
This is on the driver's side end of heater case above and to the right
of accel pedal and it is the yellow hose. Plug it up with something and
see if it returns to working, if so then leave it plugged as the cost of
repair is high and the compromise in function is minor unless you live
in a really cold place (floor air volume will be lower).
6. the vacuum canister behind the front
bumper has a vacuum leak. (usually the rubber nipple on the end is split)
These were listed in the order that I
suggest to check but Murphy's laws will likely make the solution be at
the opposite end of list from which you choose to attack.
or ACC Vent Stops Working Upon Acceleration.
General Notes. [Query:] My
friend has a '94 960 and the air stops blowing from the vents while the
car is accelerating (the a/c fan is still spinning but no air is coming
out) when ever the car reaches a steady speed it starts blowing again.
The same thing happened to me in an '90 760t and it turned out to be a
hole in the vacuum line that goes to the vacuum reservoir. However I can't
locate the reservoir in this car. Does anyone have any ideas? [Response:
Rich Kelley] The problem you describe sounds like one I've seen quite a
bit on 960's. It sounds like a ruptured diaphragm on the flapper control
solenoid. There is an illustrated, detailed repair procedure at
Vacuum Servos in ACC-Equipped 700/900 Cars. It's located
on the drivers side. Take down the knee bolster and look up on the side
of the climate control box. There are two vacuum controlled solenoids there
and the one that usually goes is the one with 2 hoses going to it. It is
very hard to get out, as it is held in place by 2, 10mm nuts on the inside
of the box.
Look Under the Hood First. [Tip
from Bob] Start by checking the vacuum supply hose under the hood.
Under-dash leaks are extremely rare. The vacuum hose for the A/C-heater
can be found under the intake near the trans dipstick tube. Look for a
small (1/8" diameter) white plastic hose. It goes from firewall near heater
hoses and winds its way to a tee with a check valve conected to a larger
hose, ending at the intake. It is common for the hose to rub through from
chafing on other hoses or wiring harnesses. When you find the leak, cut
the hose and splice with a small piece of rubber vacuum hose.
Try Cleaning It. [Tip from
Larry Jacobson] Before doing any cutting and sawing, your arm up into the
air intake that goes up in back of the glove box. You may be able to feel
bits of plastic or paper or other light foreign matter that has been sucked
into the system and is causing the flappers to not close. The vacuum motors
huff and puff and hiss trying to slam the doors on the accumulated crud.
I've had to do this twice and both times found all sorts of stuff up in
there. My wife has a habit of clipping coupons in the car. Bits of
paper fall to the footwell and some get sucked into the AC system. Makes
a racket like baseball cards in the spokes of the old Schwinn bike.
Replacing the Vacuum Motor.
[Query:] My heat/ac won't come out my vents, it will come out the defrost
and the floor vents, but not my regular vents. [Response: Dick
Riess] The vacuum motors are located on the drivers side. You need to take
down the portion under the dash and kick panel against the radio area.
These are not easily replaced (if that is what is wrong), but through a
shortcut suggested by Tom Irwin and receiving some of my mods, I
have done one on my 91 940SE. It is kind of the Don Foster approach,
in his case replacing the heater motor on 240s. There are 3 motors
and fortunately the most accessible is generally the culprit and has two
hose connections. First try a Mighty Vac and hook up a tube to each of
the connections and see if they hold a vac. If one doesn't, you have a
bad vacuum motor. Have to disconnect the hoses on the motor first, of course.
Do your diagnostics first.
[Response: Abe Crombie] To expand on what
Dick posted: The likely culprit, assuming the vacuum supply is coming
in from the engine compartment, is the floor/defrost servo. It is a double
acting (no vac centered= floor/defrost split, vac on blue hose = defrost,
vac on yellow hose = floor) and has a boot on the floor side that retains
vac on that side of diaphragm. The boot fails and you lose vac. Blocking
yellow hose fixes it simply with compromised floor air volume (floor would
be floor/defrost). All of this aforementioned stuff is usually the case
if symptom is loss on acceleration.
You don't mention whether it is a 740
or 760. The 760 has an electric vacuum valve set to left behind glove box
and a cold soldered joint on it at one of the end pins will cause no response
in any position which defaults to floor/defrost. The 740 is a rotary vacuum
switch linked to slide lever for vent selection and the hoses behind panel
(white is source) can be crushed or the feed hose (white) above accelerator
pedal at firewall can be crushed.
[Response: Abe Crombie, regarding 1990
760T with ECC: air stops coming out of any vents during turbo boost (manifold
pressure instead of vacuum), indicating a leaky push-pull vacuum servo)]
The Floor/Defrost servo you discovered leaking is sprung to return to center
when no vac is applied. This will direct air reaching this part of the
air distribution housing to the defrost and to the floor outlets. The yellow
hose applies vacuum to the side of diaphragm that will extend the servo
rod to push the door up blocking most of the defrost vent air and directing
90% +/- to floor. The seal that rides the servo rod can dislodge or just
split and you have the result you observed. Disconnecting the yellow hose
will not allow you to get full floor air. When the floor air position is
selected (by you or by the ECC logic) the air will be split between floor
and defrost. This is likely not a problem unless you have really poor leg
circulation that gives you a severe tendency to cold feet long after the
rest of your body is warm. The logic in the ECC always has the floor position
selected on this servo when it is directing air to the dash face vents
so if it leaks you lose the vac for entire system and all the doors go
their respective sprung positions.
Blower Motor. [Query:] How do I fix a squeaking blower
motor? [Response] Try removing the motor and oiling the bearings,
if they are accessible in your model motor. [Response 2: Gary Defrancesco]
In the last 6 months, I have replaced the blower motors in both of my late
'80s vintage 745Ts. The replacement kits came from IPD and include the
adaptor ring required to mount the new blower to the heater/AC box. Apparently
Volvo made a design change in the motors and the replacement ones require
a slight mod to the box. In fact the IPD kit contained the part from Volvo
for the mod. TheVolvo shop manual also describes the mod, so I am convinced
it is a Volvo design change and not an aftermarket attempt to make a "universal"
motor fit a Volvo.
My '87 745T apparently had already eaten
a motor and the mod had already been made. So replacing this motor was
a piece of cake. Just remove the trim and panels around the floor, and
remove the ECM from its mount. The ECM bracket is them easily unscrewed
for removal. The blower is just above and easily replaced with 3 screws.
I had to rewire the connector with a soldering iron, but that was no big
My '88 745T had not had its motor replaced,
so I had to do the mod. Just do the above procedure and follow the direction
for the mod that came with the motor. Needed to cut off a short plastic
drain pipe using a hack saw blade, apply some sealant to the adaptor ring,
screw it in place, and drill a vent hole. No big deal. Then mounted the
new motor, solder the wires, and close everything up.
In both cases, the squealing went away
and life quieted down a lot. One observation I made was that the cage on
the new blowers are not as deep as the OEM blowers. Hence, the cage will
not come as close to the air input port of the duct work. This may cause
less efficiently in moving air to the cabin of the car. i.e., less air
moving through the vents. Despite what I think is less air flow, I still
get plenty of heat and AC. At least the squealing is gone, so I can't complain.
Blower Motor Replacement. [Query:] [Response
1: Kevin Lawler] If you have done several 240's you should be able
to do a 740 blower motor with your eyes closed! Remove the under dash hush
panel on the passenger side. Next remove the right side kick panel over
the fuel ecu, then remove the 2 screws holding the ecu and remove the ecu.
next remove the 3 screws holding the ECU bracket, and remove the bracket.
Now remove the 5 screws holding the blower motor in place and remove the
blower motor. Remove the ground wire from the old motor and
unplug the power wire. Install new motor in reverse order. Some cutting
and modification may be required depending on the style of the motor. I
have done several of these, always in less than 1 Hr. [Response 2: Ney]
The only important tip is to remember to disconnect the battery, because
the ECU may need to be removed in order to gain access to the blower.
Also remember the small black wire with self-tapping screw is ground.
700 Blower Motor Only Runs "High". [Query] Fan switch only works
on 5, no 1,2,3,4,? Is it the switch or is there a resistor pack or
can it be the motor? [Response: Abe Crombie] There are two things
that come to mind dependent on how a 92 is wired. There may be a blower
relay on the case behind glove box. It passes all the current from resistor
to blower but on high the relay is energized and its contact switches over
and feeds direct 12 v to blower saving the switch from having to carry
the high amperage. If the contacts on the lower speed side are burnt this
failure would occur. The other is the resistor itself. I believe a 92 has
this feature but it might not have occured until 93, anyway, the resistor
may have a temp fuse integrated into it that will go open if the blower
resistor has debris around it or if the blower motor drags. Either of these
two will make the resistor get hot enough to trip the temp fuse. If the
resistor has the temp fuse it will be a green ceramic covered resistor
and the temp fuse will be adjacent to ceramic core. It is a silver 3/16"
cylinder with tapered ends , one of which is white. In either case i can
tell you w/o too much doubt that you will have to go behind glove box as
the relay is there and the resistor is stuck into the blower case in that
Blower Motors for 7XX pre-1990. [Note: Latest comment: There is no
GM part equivalent to the Volvo blower motor for 1990 and later 7xx/9xx.
The part may work fine in an earlier Volvo. The Volvo replacement part
has been redesigned from the original 1990 part so you can't just get the
blower motor assembly - you need the assembly, a new plastic mounting plate,
and according to parts person, a new resistor added to the switch.]
[First comment: GM mid-80's blower motors
for AC Chevy Citations are exact replacements. Also: look for an '81 Delta
88 w/ air conditioning blower motor. Also: The replacement for the 760
series fan motor is a standard GM fan motor. The NAPA part number is 455-1076.
Also: fan motor for a '87 760. The clerk responded, $57.94 and we'll have
to order it. Then, I said ok, Try a '83 Chevy Impala with AC. In stock
and $17.99 with lifetime warranty.]
The reason the original fan failed became
quite apparent in today's rain. Water showed up around the new fan. Apparently
the 740 has a tendency to leak on the passenger's side with the water ending
up in the plastic basin that the fan sets in. [Note: See Volvo
TSB for a fix for this problem.]
[Second Comment:] After posting an e-mail
question regarding heater blower motors on the Swedishbricks mailing list,
I received a response from Bill Cheb that he rebuilds heater blower motors
and adds ball bearings which should add an extra several hundred thousand
miles to their endurance. Bill was easily accessible via e-mail at email@example.com.
He promptly responded with information on how to order. His delivery was
prompt and included detailed instructions on how to install the new motor.
The total cost including delivery was $125.00.
in Ventilation System at Blower Motor. [Query:] The blower motor
in my 700 has been changed (for the cheaper GM unit) and has filled up
with water from somewhere twice. Any thoughts as to where this is coming
from or how to prevent it from filling up with water? [Response:]
I had a similar problem; under the cowling (just forward of the windshield,
aft of the hood) there is a black plastic shroud that covers the air intake
(actually it's just the top of the motor housing) to the blower motor.
In my brick, the plastic had detached from the windshield edge and hung
down, allowing water to pour directly into the blower. One of the
few bad designs on the 7xx brick, IMHO.
[Editor's Note:] Check that the
blower motor mount in the air plenum is not cracked.
A/C Performance: Diagnosis. [Query:] I have a 1993 945 turbo.
The air conditioner (134a) works ok on the highway. when it is less than
90 degrees outside, but only makes the car bearable in city driving. I
checked the charge level and it appears to be fine. Does anyone have any
ideas? [Response: Abe Crombie] I had a car like yours and the a/c
was fine in the southeast US summer. The problem could be any one of several
possibilities like heater valve not being closed at full cold position
of the temperature control, partially blocked condenser, cooling fans not
working correctly, etc. The only way to know you have the right charge
level is to recover and then refill a/c system. The hot water valve
should be getting vacuum via a vacuum switch on the heater control when
the temperature knob is turned that last little bump to the left. Bugs
and stuff will block the condenser over time and this will make performance
suffer even more on R134a systems. The electric fans must work properly
for the same reasons.
[Query] Need help with my '91 740
Turbo Wagon A/C system. It works great when Im on the highway (ie. speed
greater than 40 mph) but when I slow down or stop I lose cooling. I believe
that I am not getting good condensing action even though there is a belt
driven fan on the engine. I suspect that the small electric fan in front
of the radiator needs to come on with the A/C. [Response: Rob Bareiss]
YES, your electric fan is supposed to be on AT ALL TIMES when the AC is
running. My guess is if you pull your grille out, and reach in there, you'll
find it does not turn freely. So the motor probably burned out when it
seized up. Just had three of them do that, all on 740's like yours. A good
used one can likely be found at a junkyard- new one is $211 from Volvo
(!!!!). It's probably worthwhile to have your AC system leak checked now
as well- if it's leaking at all, consider a conversion kit to R134 refrigerant.
It's at the point now that it's almost cheaper to convert it than to recharge
with R12. A kit costs $61 from Volvo, and R134 ought to be less than $50.
If your system was fully discharged, a full charge of R12 would be over
$110. A partial charge would be cheaper, and since yours works mostly,
it's probably got close to a full charge in it. Keep in mind also
that you'll be getting a new expansion valve and receiver/dryer with the
Volvo kit, so it ought to be pretty efficient for years.
conditioning: R134 change from R12 in Volvo cars.
Basics on Air Conditioning R134 Retrofit.
[Tip from Larry Carley, Underhood Service, April 1999]
In most instances and in most vehicles,
a "basic" R134 retrofit procedure is all thatís required to retrofit an
air conditioning system. By basic, we mean recovering any residual R-12
that may still be in the system, draining out the old mineral oil, replacing
the accumulator or receiver/dryer, and then evacuating the system to purge
air and moisture, adding the specified amount of POE oil for the compressor
and recharging the system to 85 to 90 percent of its original capacity
Volvo was the first auto maker to approve
POE oil (P/N 1161442-7) for R-134a retrofits. Volvo retrofit kits include
a new receiver/dryer and O-rings (color coded yellow) for the expansion
valve, and a new expansion valve or orifice tube. The following kits
are available from Volvo:
9145660-8 -- covers 1985-92 740 models,
1983-87 760 models, 1991-92 940 models, 1989-91 780 models and1983-86 700
Volvo says the system should be evacuated
for at least 50 minutes following recovery of the R-12 and component replacement
to pull out as much residual R-12 as possible. Volvo also says the shaft
seals on Sanden 508 and 510 compressors must be replaced when converting
to R-134a. The new seal is P/N 9134344-2.
9145666-5 -- covers 1991-92 240 models
9134808-6 -- covers 1975-90 200 models
9145661-6 -- covers 1988-90 760 models,
1991 940SE and 1992 960 models.
If the compressor is being replaced, it
should be filled with POE oil through the fill plug only, never through
the inlet or outlet ports. Also, if the compressor is being replaced, Volvo
says not to add oil to the receiver/dryer.
[How to retrofit R134 into R12
systems:] Great website from Dave Urban showing the instructions and illustrations
for the Volvo retrofit kit for 7xx cars and Dave's annotated comments from
his own changeover: http://www.prismnet.com/~davurban/AC_RETROFIT/Page_1.html
If you're like me, you don't want that
to happen when it's really cold outside. So that would require the addition
of a temp cut-out switch to the above mentioned two-input relay. In addition,
having the aux fan on at highway speed actually will DECREASE cooling performance
because the fan is "basically in the way". So add a speed sensor cut out
to the above circuitry. Now you've basically got most of what the more
modern 9x0 (1993-) cars have as standard. As a first test for you, skip
all of this and try wiring things up so that the aux cooling fan comes
on whenever the compressor comes on. You can fake this by connecting the
two wires at the temp sensor up at the top right corner of the radiator
(effectively bypassing the temp switch itself.) Use a paper clip or something,
wrap it with tape, close the hood and drive around and see if this makes
any difference. If this doesn't help I'm out of ideas.
If it does help somewhat (you'll obviously
need some temp gauges to measure all this), there's always the option of
grafting the 780 aux cooling fan onto your 740. Volvo has a kit for this,
which I imagine is pretty pricey since it includes a brand new fan etc.,
but they needed it for markets such as Arizona, even BEFORE going to 134a!
As far as I remember the kit doesn't include any of the logic suggested
above, so I'm not sure it'll do anything unless some sort of A/C triggering
is added as well.
[Tips Ex Post Facto.] My turn to share some
info since I have just finished my part of the 134A conversion (vacuum/charge
to be done at the shop next Tuesday. Here are my comments and advice:
[More how-to:] About a month ago, I retrofitted
my wife's 88 765T to R134a, using the Volvo retrofit kit, which contains
a new receiver-dryer, orifice tube, o-rings, and ester oil. I did it right.
First, I had the system evacuated. Then, using compressed air, I blew out
all the lines. Then I installed the new receiver-dryer and orifice tube,
and then I pulled off the compressor (that was a job!) so I could empty
the old oil out and add the new oil. Volvo gives you the oil for this,
but doesn't tell you how you're supposed to change the oil without removing
the compressor -- and apparently they don't expect you to, since they don't
include o-rings for the hoses. What, do some Volvo compressors have a drain
plug on the bottom? Mine has a fill plug on top, but no drain hole on the
bottom. Anyway, I took it back to the shop, had them draw down a vacuum
on the system, then recharge it with R134a (it takes LESS R134a, BTW).
The result? 41 degrees F at the vent -- which is Volvo spec for the '88
765T. This was with the car sitting at the A/C shop, just idling, too.
[Lack of adequate cooling after retrofit:]
I would have to say that the person responsible for updating this particular
7xx system missed something. I have performed probably 25 of these conversions
on 200 and 7/900 vehicles using the OEM kits provided by Volvo and all
of them have worked as well or better than the R12. The secret is to use
the proper amount of 134, if you overcharge or undercharge, the cooling
output is diminished. In our shop we use the Snap-On charge station that
charges the system by dialing in the amount digitally and forces it in
by the kg or ounce. The only way to get the proper charge is to weigh the
refrigerant before installation; no way you can guess and be accurate.
The lack of cooling at idle could be from over/undercharged. Partially
blocked condenser/radiator (bugs, dirt). Inoperative clutch fan or auxiliary
fan. Too much oil in the system, wrong orifice tube (should be changed
to a tan one), weak ac compressor, blocked accumulator or ac cycle switch
set too high. The 200's are a different story but I have never had a complaint
for insufficient cooling here in Georgia, even from a 245 owner. The new
evaporator that comes in the Volvo kit is about 30% larger in surface area
and the cooling capacity seems to be better than R12. Just for comparison
purposes: Our shop gets $187.00 to convert an operating 12 system to 134
on a 7/900.(parts and labor) $375.00 for a 200. (parts and labor).
I recently did the same conversion on
my 1989 745GL. I'm not terribly happy with the performance at idle either.
After some experimenting I've decided there are a few things that can be
done to improve things, none of which I have implemented yet...First thing
is to make sure the fan clutch is in good working order. Second problem
is if your mechanic put in TOO MUCH 134a! Problem is that the Volvo conversion
kit only includes a low-side 134 filler port. There's no way to measure
the high side using the new SAE 134 fittings. Because of this there's no
way for the mechanic to know what's enough refrigerant in the system other
than looking at the dials at fill time. The third thing that needs attention
is the all too rudimentary aux cooling fan setup. In stock, on 7xx cars
(excl 760 1988-), the cooling fan in front of the condenser is triggered
by a temp sensor in the radiator. That's all well and good, but doesn't
do squat about the condenser cooling. What's needed is the aux fan being
ON whenever the compressor is on. A simple relay that lets either the engine
coolant temp OR the compressor turn on the aux fan would be a good first
line of defense. This would probably be sufficient for most apps in most
parts of the world. BUT, this will also mean that the aux fan comes on
when the system is put into DEFROST mode, as the A/C is always on then
to dry the air.
You get a lot of hardware in the conversion
kit for the money
Make sure you ask for the instructions
a few times when ordering. (Rusty at RPR was able to fax me 27 pages before
I finished). Basically the same instructions that you can get off the www
but a bit more clear and detailed. I have them stored in a file (RightFax)
and can email to anyone who wants them.
The R134 conversion is not that hard.
I'm not sure how to get to the measured torques using open ended wrenches;
I went by feel.
The toughest part of the job was replacing
the compressor. Mine was a back breaking job since it was so low: below
alt and P/S pump. The lines running to the compressor were tough to get
off and on (seemed to be too much bending involved. Perhaps mine were not
Be very careful threading lines into the
soft Aluminum threads on the compressor. Go by hand as much as possible
before using the wrenches.
The electrical connector for the new Seltec
compressor was not the right size for the old line.
I had to file the hole in the compressor
wire holder that bolts into one the the compressor mounts so it would fit.
The Seltec compressor did not have a drain
so I was advised by Rusty (RPR) to turn upside down and rotate to get fluid
out of the inlet/outlet. Ester oild was added to the receiver/dryer only
I'd consider ordering all new hoses if
I did it again (hopefully I'll get by)
I do not know why the kit did not come
with new seals for the whole system: hopefully not needed?
Air Conditioning R134a Conversion:
Tips from Lee Fox RE: 740 AC conversion and variable orifice tube.
I just got done converting my wife's 1990
740GL from R-12 to R-134a and thought I would report on the process.
Many thanks to David Urban's most helpful web page describing the entire
procedure. He gave me the encouragement to try it myself and he saved me
at least $100. Visit his page at http://www.prismnet.com/~davurban/AC_RETROFIT/Page_1.html
I purchased the conversion kit from Brentwood
Volvo for about $50, but could not get one of the connections on the old
accumulator off, so had to buy the supplemental kit for pre-1988 models
for an additional $28. My system had leaked out all of the old R-12 from
the original factory fill valve. The folks at the dealer said that this
was common and now install the supplemental kit whenever they do the conversion.
Following David's instructions, the changeover was easy, taking less than
one hour. I rented an AC vacuum pump and gauges for about $25 and bought
three cans of R134a plus some leak detector (I wanted to make sure I didn't
have a leak elsewhere) and a charge hose for about $30 from Auto Zone.
You have to evacuate the system for about
an hour and it took about another hour to get it charged up. I had to jumper
the low pressure switch to get the compressor going to suck in the first
can. When I returned the vacuum pump I had to wipe to condensation from
my glasses walking into the store - it was that cold inside the car!
I wish I had heard about the variable
orifice valve tubes before I converted. It sounds like a good idea. You
can find out about them at http://www.aircondition.com/vov/
This is also a great site to learn all about automotive air conditioning.
You can even take the test online to become EPA certified to buy R12.
In summary, I would recommend the conversion
to anyone who needs to fix an ailing AC. We be chillin'
[Tips from A/C UPDATE: Retrofit Vs. Recharge,
Retrofitting Techniques, Improving Cooling Performance & Alternative
Refrigerants, Larry Carley, ImportCar, May 2000 (Excerpts)]:
One way to improve cooling performance
when retrofitting an older R-12 system to R-134a is to install a "variable
valve" orifice tube in place of the standard fixed orifice tube. These
aftermarket variable orifice tubes allow the flow rate through the valve
to change for better cooling at idle and low speeds. Such a valve can lower
the A/C outlet air temperature by as much as 5 to 8 degrees, which can
make quite a difference if the vehicle is crawling along in stop-and-go
city traffic. Installing a larger or more efficient condenser can
also help compensate for losses in cooling efficiency with R-134a. If the
original condenser or evaporator is being replaced because of a leak, damage
or defect, make sure the replacement unit has the same or better BTU rating.
Some aftermarket replacement condensers and evaporators may not deliver
the same cooling performance, and create a problem your customer didnít
When a compressor fails, it can throw
metallic debris into the system. Most of the junk ends up in the bottom
of the condenser, but some of it can also be blown back into the suction
hose. Flushing the condenser, hoses and evaporator with refrigerant or
an approved solvent may remove most of the debris, but parallel flow condensers
cannot be flushed effectively. Replacement is often recommended if debris
is found in the system. Most experts also recommend installing an in-line
filter (high side and/or low side) to protect the replacement compressor
and orifice tube or expansion valve. There are also filter screens that
can be installed in the suction line to prevent any debris from reentering
Itís important to remember that R-134a
or any other alternative refrigerant cannot be mixed with R-12 or used
to top off an R-12 system. If an A/C system still contains any R-12 at
all, it must be removed using approved recovery equipment (venting is not
allowed) before a new refrigerant is added to the system. This is
an absolute must to prevent cross-contamination of refrigerants and cooling
performance problems. R-134a and mineral oil wonít mix. So if somebody
recharges an R-12 system with R-134a and doesnít add a compatible lubricant,
the compressor will soon fail.
versus Refrigerant Alternatives: General Opinions. There is a lot of
misinformation (and intentional disinformation) flushing through the car
hobby and repair industry about the state of auto A/C in 1997. We see people
rushing to convert their perfectly good R12 systems to R134a, we see people
demanding R134a systems for new installations, and we see charlatans pushing
ineffective, dangerous, and/or non-approved refrigerants and repair techniques.
Worse yet, we see even bigger charlatans claiming that R134a is almost
magical in its ability to go into any system, cool as well as R12, never
create any compatibility problems, insulate your house, filter your coffee,
and get your clothes whiter, brighter, longer. (Well, okay, maybe not those
last three, but you get the point. R134a is being passed off as some kind
of magic bullet for A/C systems.) The fact is that 134a, while it is nearly
universally used in North America and many other countries as the OE refrigerant
in '93 and newer cars, has numerous significant disadvantages over other
[Another Comment:] It is not a good idea
to convert your R12 car to R134a or any of the R134a-based refrigerants
(FRIGC and Freeze-12 come to mind). They are, relatively speaking, extremely
inefficient refrigerants. Also, they are HIGHLY incompatible with R12-type
oil. They operate at radically different pressures, so calibration of R12
expansion valves won't be optimal. Also, since 134a is so inefficient,
one must use larger compressors, condensers, and evaporators to get the
same level of cooling as from an R12 system. This is difficult and expensive
to do on an existing system, so you get much less cooling with 134a. Perhaps
most troubling is that R134a, unlike most other refrigerants, is not chemically
inert. It is reactive, and has been shown to cause reproductive damage
and is a suspected carcinogen.
Now that I have detailed some of the disadvantages
of converting, let me outline what you would need to do to convert to 134a
so as not to shell any of the components [Editor's note: see above remarks
for Volvo-specific information and retrofit kits.] You're going to need:
Barrier-style hoses (The R12 hoses are
permeable to the smaller R134a molecule)
All new seals and O-rings (ditto above)
A rebuild or thorough flush of your compressor.
Which one you will need depends on the design of the compressor. Early
Chrysler, York and Tecumseh compressors, for instance, use an oil sump
and pump which cannot be "flushed" of oil like non-sump type designs, and
because 134a is so violently incompatible with 12-type oil, you have to
get ALL of the old oil out.)
New receiver-dryer with XH7 or XH9 desiccant
In addition, you're going to want to purchase
a new condenser of the "manifold" or "parallel-flow" design to try to get
as much condensing surface as possible for the refrigerant. The inefficient
134a, under high-demand situations, must literally be *forced* to condense.
The serpentine condensers used in R12 systems do not have this capability.
People often cite low cost of the R134a
refrigerant itself as a reason for converting. Have a look at that list
above and it becomes readily apparent that $80 worth of R12 vs. $20 worth
of R134a is an irrelevant comparison.
There are other legal, safe, effective
and efficient options if you have decided, for whatever which reason, to
convert your system to a non-12 refrigerant (more on this later). Various
companies have brought various refrigerants to market. Many of them have
been minimally tested, have disadvantages similar to 134a, and/or other
deployment difficulties. For instance, a lot of the new refrigerants have
a very difficult time carrying any kind of oil back to the compressor.
R12 has very good oil carrying capability, so the vast majority of existing
compressor designs are meant for use with a refrigerant that will bring
the oil back and lubricate the compressor. New oils have been developed
to work reasonably well with the new refrigerants, but industry data confirm
that compressor failure rates are up since the advent of refrigerants that
don't carry oil as readily.
My own research and testing has turned
up two very interesting refrigerants that seem to work extremely well,
with minimal deployment difficulties. Those are R406a, and GHG-X4. Both
refrigerants were invented by a Professor George Goble of Perdue University
in Indiana. I don't work for the company, I don't sell the stuff, I have
no association with Mr. Goble or anyone else on his refrigerant staff,
except I've communicated with them by e-mail a few times. I point this
out to indicate that I'm not trying to sell something, don't have any particular
agenda or ulterior motive, etc.
Here is a rundown of some of the advantages
of these two products as conversion refrigerants (actually, EPA's preferred
term is "substitute" or "replacement" refrigerants.)
They are MORE efficient than 12, yet they
operate at similar pressures, so the expansion valve calibration will remain
optimal and your existing condenser and evaporator will function MORE than
adequately. (improvement is usually quite quantifiable with a good A/C
thermometer in the center outlet. Air outlet temps are usually 2 to 12
degrees colder than with 12.)
They are completely compatible with R12
type oil, so no system flush or compressor rebuild.
Both 406a and X4 have passed all UL, DOT,
EPA and ASHRAE tests for safety and utility in mobile and non-mobile systems.
They are certified nonflammable.
Are there any disadvantages? Yes, and
here they are:
It is a ternary zeotrope, which means
it is made of three components. This is an advantage AND a disadvantage:
Leaking systems theoretically must be completely evacuated and recharged.
Also, charging must be done in a LIQUID CHARGE fashion. (Note, this also
explains the improved efficiency. The three factions boil/condense at slightly
different temperatures. This is known as a temperature "glide" and effectively
increases the usable condenser/evaporator area, creating the increase in
You still need barrier hoses, because
R12 type hoses are permeable to the smaller R406a factions' molecules.
New fittings and system labels are still
legally required, since EPA has determined that each individual refrigerant
product must have its own set of uniquely-threaded fittings. Adaptors and
replacement fittings are available. (Note, this is a legal requirement.
Physically and chemically, these two Rs are completely miscible and compatible
Shops using R406a and X4 may be more difficult
to find than those using 134a. Production and distribution of 406a and
X4 has been ramping up steadily for the past several years.
Now I have to ask YOU a question: Why are
you converting to anything or demanding a non-12 refrigerant? R12 is still
around, you know, and anyone who tells you otherwise is lying or ill-informed.
There is plenty of it in the US. There is MORE than plenty of it in the
US. And there will be for a very long time. The best policy if you've a
working R12 system is to keep it an R12 system.
Some will tell you that R134a is the only
legal refrigerant. That's wrong. Go to the EPA SNAP (Significant New <refrigerant>
Alternatives Plan) homepage and see for yourself that many new refrigerants,
including 406a and GHG-X4 have passed all the safety tests, are certified
Some will tell you that 134a "moves more
heat" than R12. That's also wrong. Some will tell you that no flush, rebuild,
or anything else is needed when converting to 134a, and that you can just
drop 134a into an existing system. For most systems, That's dangerously
Information on conversions and refrigerant
alternatives can be found at:
Compressor Failure: Electrical Ground. [Tip from Bob Simon] Last
week I posted a problem with my A/C abruptly stopping. I had checked the
fuse, but had not looked closely enough at the wires leading to the compressor.
Turns out that the ground wire for the compressor was corroded and the
connection failed. A new connector was crimped on and re fastened to the
compressor and it seems all is well now. Go figure. At least it wasn't
a clutch or solenoid.
Clutch Failing. [Symptom:] My '86 760T is losing it's compressor clutch.
What does it take to change this clutch? [Diagnosis:] First is it really
the clutch?1) If the compressor is starting to seize internally that will
cause the clutch to slip and burn but the fix is a new compressor. 2) Is
it the pulley bearing making noise? That requires a special tool to hold
the front plate while you unscrew the big nut on the input shaft. The clutch
and pulley then press off. You need to remove the freon since you're working
at the front seal. 3) If the clutch is really worn out get the special
tool and press it off. You can get another at a u-pull-it yard. However
compressor rebuilts are not that expensive and really once you're at a
u-pull-it yard the cost of a clutch vs a compressor is about the same.
So I'd say replace compressor, either used or rebuilt.
Clutch Removal [Tip from
Loren Rux] There are three threaded holes for 5mm bolts in the clutch
plate, and I just assumed they were for removing the clutch plate by evenly
screwing in three bolts, forcing the plate off the shaft. Whether
or not that is the purpose of the threaded holes, it worked. After
the plate was about ½ inch out, it came easily.
the AC Clutch on an '89 760 [Query:] The compressor turns
by hand OK but the clutch is burnt white and occasionally screeches.
I have the belt off and the center bolt out
but cannot get the pulley to move.
Gentle prying has not moved it. Any suggestions?
[Response:] Keep prying. There is
a special tool (naturally) but it just pushes it off by attaching to the
threaded fitting in the hub of the face of the clutch. Once that is off,
there is a snap ring at the front which holds the pulley and bearing on.
Tapping on the pulley will slowly move the assembly off the front of the
compressor. Then there are 3 Phillips head screws which hold the coil on
to the front of the compressor. These round off easily so try tapping on
them with a 3/8" #2 phillips bit before trying to turn them.
or Replace Diesel Kiki A/C Compressor? [Query] My '87 700 has
a Diesel Kiki a/c compressor that has seized. Is it rebuildable (by me?)
or smarter to just remove & replace? Are rebuilts available?
Are they good as new? [Response: Tom Irwin] In the years I worked
in aftermarket I probably bought between 50,000 and 100,000 Diesel Kiki's",
as rebuildable cores. What can I tell you... Well, in general they
are CHEAPLY built and not very reliable compared to Nippon-Denso, Panasonic,
etc. "Is it rebuildable (by me?)" No. "Are rebuilts available?"
TONS! EVERYWHERE! "Are they good as new?" Sometimes they are
better...the aftermarket KNOWS which components fail and endeavor to improve
the unit. Look for who manufactured it... Murray/Moog, Four Seasons,
AC Plus, are all EXCELLENT rebuilds. ASK the parts guy who makes
their private label stuff "Can the clutch be replaced without discharging
the system?" Yes. One last note... Diesel Kiki's, that were converted
to 134a are shit. Since you are going whole hog... get a 134a pump...new
receiver/drier... do it right. 12 is just to much hassle. [Response:
Lamar] You can get a new one for just over $200 at Autozone or Advance.
They come ready to use either R-12 or R-134a. I just replaced one on an
Hints in Hot Weather in Post-92 Models. 93 and later models that have
R134A refrigerant as factory fill have a compressor high temp shutdown
switch at compressor clutch circuit on comp. This can make compressor
go off for 5-10 minutes if one of two things is happening:
1. refrigerant level is getting
low. The un-boiled refrigerant on a full system that returns to compressor
will cool it. If it's low this doesn't occur and off it goes.
2. If it's over 100 F outside the
a/c shutdown will occur due to compressor getting too hot. You can prevent
this manually selecting recirc when it's this hot as the re-circulated
air entering evaporator will allow the return refrigerant back to compressor
to cool it down enough to prevent this. Don't let it stay on recirc forever
as this will lead to a much increased likelihood of a/c odors. Turn it
off recirc at night or when the temp gets back to normal (if it ever does
Odor from A/C System. [Tip from Editor] I have had a similar problem
on both my 1990 745 and 1995 944: mildew-like odors from the air conditioning
system, especially when starting the car again after it has been sitting
for some time in the heat and humidity. To prevent it, limit
your use of the recirculation function and turn the a/c selector to "vent"
about three blocks before you reach each destination, allowing the
evaporator to dry out before shutdown.
You have two effective means of fixing
the odor problem once it starts:
a. [For a mild case of mildew; evaporator
and plenum don't have accumulated leaves, etc.] Buy a spray can of BG Frigi-Fresh.
This is an evaporator disinfectant made just for a/c systems by BG, the
same people who make BG44K. Contact BG for a local distributor (http://www.bgprod.com/).
A small can, sufficient for many treatments, costs approximately $8. Remove
the passenger kickpanel under the glovebox and the right side kickpanel
covering the computer module. You will now be able to see the air plenum
and the blower motor. Near the blower motor is the blower resistor with
wires going into it. Using a 1/4 inch drill, carefully drill a hole in
the plastic plenum about one inch to the bottom-left of the resistor, sufficient
to allow you to maneuver the spray tube of the can so as to spray toward
the driver-side of the plenum. Approximately two inches to the left of
the hole is the evaporator core, which is around 8 inches wide and 8 inches
tall, oriented on the long axis of the car. (If you want to inspect the
system, remove the glove box and blower resistor.) Turn on the engine,
engage the a/c system with the blower on "3". Spray a generous dose of
FF through the drilled hole all over the evaporator core. Turn off the
engine and let the treatment dry. Cover the hole with duct tape and re-assemble
the kickwell. You will have a disinfectant odor for about a week, and the
treatment should last a good part of the season. The hole will make it
easy to reapply the FF next time. The whole job should take about an hour.
b. [For a worse case of mildew, along
with accumulated crud in the system.] Same disassembly procedure as above,
only remove the blower motor and lower plenum assembly as a unit.. This
requires removing the glove box and engine computer to secure good access,
then the motor and resistor wires, then around eight screws holding the
lower plenum on. Using a shop vac, remove accumulated crud (leaves, dust,
etc.) and swab out the plenum with disinfectant. Clean the foam filter
on the downwind side of the evap core. Either use a treatment of
Frigi-fresh on the evaporator as above, or go the whole nine yards with
some "Airsept", a cooling coil coating treatment applied by spray (such
as a garden sprayer.) This costs around $60 and can be bought from Volvo
dealers as part number 000116154 or from GM dealers ("GM Cooling Coil Treatment").
I haven't used it, but it is supposed to result in a coating on the evaporator
coils that inhibits mold growth. GM claims good results. This procedure
is described in great detail in the Volvo shop manual for heating/air/conditioning
systems. While you are at it, make sure as well that the cowl leaf
screen is in place to limit ingress of crud which will be caught in the
plenum and result in mold growth.
Water Leaks: Clogged Evaporator Drain. [Tips by Steve Seekins,
courtesy of Guri Roesijadi] [Query:] Water is leaking into
my front footwells and soaking the carpets. How do I diagnose this?
[Response:] The likely culprit for the wet carpets is a plugged
evaporator drain - look on the firewall, passenger side - you should see
the drain outlet there - may be flush with the firewall, or there may be
a tube attached that runs down toward the frame rail. The plastic
casting for the lower air-box half actually includes the drain spigot.
It is likely clogged with leaf debris or other stuff. Check the air
intake behind the hood - there should be a screen under the slots and bonded
to the bottom of the slots. If it has come loose, it lets stuff into
the air box. To repair, you need to remove the cowl piece -three
bolts along front edge under rear edge of hood (no need to remove hood)
and remove the wiper blades and rubber pieces. Middle bolt is usually
hidden behind the rubber weather strip. Cowl moves forward and comes
off. There are plastic pins on each side that fit into slots on the
cowl. It also fits into clips along bottom edge of windshield.
Screen is fastened to underside of cowl
with some sticky black RTV type stuff. Getting the cowl back in is
a bit more difficult than getting it out. First, often the small
plastic pins at the ends break - they are sort of a blind plastic rivet
affair - good to have one or two new ones on hand. Second, getting the
cowl properly lodged under the clips at the lower edge of W/S can be tricky
and if you don't, the cowl will not lay down against the lower edge of
w/s properly. Get the plastic leaf/snow guard from Volvo that goes over
the vent opening - helps keep the leaves and crud out.
PITA to try to dissassemble the air box,
but you might try removing the blower motor (which may be trashed if the
lower bearing has been running in water!). Blower is held in with
4 or 5 screws, one electrical connector, ground lead, and there is a motor
cooling air tube. Motor housing is usually sealed with RTV to prevent
any air leaks. To get it out, remove panel above passenger feet,
remove the right side hard panel, unplug and remove computer and the computer
bracket. You should now have enough space to get it out - 8mm nut
driver on flex extension is helpful. Remove the tube from the motor
housing and inspect the lower bearing - any signs of water or rust in there
likely means lower bearing is trashed and motor will soon fail. Then
use air nozzle to blow in to the drain and force any debris/leaves out
through the blower motor hole, or try clearing with piece of coat hanger.
Just be careful not to damage the A/C unit inside. Of course, the
air method may only move the debris away from the drain temporarily.
Not Working. [Query:] The heater in my 745TD still thinks it's
summer... The engine itself heats up in a normal period of time, coolant
temperature is at a normal level. The coolant system builds up pressure
in the expansion tank. This morning I put a piece of cardboard in front
of the radiator. I still got cold feet, so the thermostat is OK,
right? The hoses that go towards the heating element are fairly warm.
The air from the top dash vents is not very warm and even on position 4
the flow is rather weak. The middle vents are warmer and the flowrate is
good. The flowrate below is nearly neglible and the temperature is
just above 0 C.
[Response: Dennis Hamblet]
1. Your thermostat needs replacement and
your dash gauge is not reading correctly. Cheap and easy to put in a new
thermostat to confirm.
2. Your heater core has a deposit of sediment
or minerals restricting the flow of warm coolant in which case the system
may benefit from a backflush.
3. The heater control valve has a blockage
restricting flow and may be in need of replacement;
4. You have a vacuum leak which causes
the heat vent control to work improperly.
Core Leaking? [Query:] I guess that the heater core in my 86
740 Turbo wagon is leaking cause I have antifreeze on the front floor.
Is this as nasty a job as it looks? [Response:] The heater core is
a pain in the @#%&* to replace. Try to find out where the coolant is
coming from. Usually if the core goes bad you get a coolant mist on the
windshield with the defrosters on , and you get some drainage from the
A/C condensate line. The control valve may have spring a leak. Check
that carefully, along with the hoses, before yanking the core out.
[Tips from Bob] I have done 2 heater cores on 700 series cars. It
is rather labor intensive. You have to take apart the lower half of the
dash and partially disassemble the heater case. The heater core is on the
left lower side of the case. You need to remove radio, fusebox, left side
center console panel, bracket that holds fusebox,bottom left side air distributon
box. When you can finally see the heater core, it looks like a hand grenade
went off in your car. If you have done a lot of 700 dash/interior work
and are VERY familiar with it, the job takes about 5 hours. If you are
not familiar, plan on a weekend. You MUST have a good shop manual. I strongly
recommend getting the Volvo OEM climate unit manual (see Volvo
Climate Control A/C Not Working. [Query] Our 940's manual
climate control AC problem is in the control circuit. The 700/900 FAQ shows
the relay cluster, but there is no AC or ACC relay shown. Does anybody
know where it might be on a '94 940 (non Turbo), Halifax assembly? A relay
socket would be a good place to trace further, and, the car being a Volvo,
the trouble could even be the relay!
[Response: Patrick Paul] If you have power
to the pressure switch then all components before that are OK as far as
turning the power supply off and on. You can go to the electrical
connector on the compressor and check if you have power there. If
yes, then your problem is the control unit. Any loose solder on the
control board lets just enough current flow for you to get a voltage reading.
But the amps are not enough to turn the compressor on. The
repair is very easy once you find that spot in your control unit circuit
board. [Response: Abe Crombie] The control panel with the knobs
is the control unit. The electronics are part of the control. The a/c compressor
relay on the 91-95 740/940 with the manual a/c system is integral with
the control assembly. The relay usually isn't the problem, it is the solder
joints from the connector to PC board or PC board to relay pins. The relay
is soldered to the circuit board. When you remove the control panel you
will see the metal enclosure for PC board. [Response: James Abercrombie]
The time delay for compressor start is integral in the electronics of this
board so there can be a failure of the circuit that stops the a/c compressor
that is not related to the solder connections, but this is very rare.
Re-Soldering the Control Unit PC Board.
[Response: Philip] We had intermittant
AC problems on our 94 940 turbo that were cured by resoldering a bad solder
on the control board (behind the switches). As usual you need a magnifying
glass to see the bad solder. Ours looked OK, but had a dark circle aound
the outside. Re-soldered it and save $400 for a new one. [Response:
James Abercrombie] There are no service parts for this unit. The
wave solder process demons have struck this unit. The solder cracks at
the points where the high current load is passed through the PC board connections.
Soldering is usually all it takes.
[Tips: Patric Paul] Remove the radio.
Take off the cover on the front of the control unit. It just clips
on. There are 2 or 4 screws that hold the CU in place; take them
out and disconnect the CU. Remove the silver panel (clips and screws).
Take out the screws for the circuit board and examine it. The faulty
solder spot is in the lower half, a little to the left. Take your
time and you will get it done. Don't overheat the circuit board
[Response: Brian Oliver] The A/C
failure was caused by the solder joint between the AC relay and the HVAC
contoller's circuit board, as suggested. All this stuff is integral with
the HVAC control panel in the dash. Once you have the panel on your
bench (or kitchen table in my case), remove the black plastic cover to
expose the circuit board mounting screws, take out the circuit board, and
look for the cracked solder joint. Mine was easy to see, but I do know
that they are not always so. Resolder, reassemble, install in car, and
enjoy. These HVAC control panels can be fixed as long as you don't need
parts. They are at least as repairable as Bosch relays. They are sturdily
built, too except for this one badly designed trace on the circuit board.
I am a physicist by training, but years of working in failure analysis
in the telecommunications industry tells me that the solder joint in question
is under-engineered. I just scraped away some solder mask to allow greater
wetting area, which I think will help prevent future failures.
Heater Control Not Working. [Query:] Re 1987 765T; while at the
dealer getting a new transmission put in, I also had them install a new
heater control valve. The automatic climate control system will not put
out any heat, at any setting...even with defroster on. The dealer believes
the problem is a vacuum connection in dash. The heater control valve is
not getting vacuum. Previously I pulled the glove box out and checked the
vacuum hose and shutter doors there...they seem fine. The A/C works fine.
Dealer says it is about an hourís labor to look in the center dash to find
the vacuum problem. Can I do this myself? [Response:] Several things
could have happened, most likely because the dealer who put in the new
trans broke a vacuum line or crimped one somewhere...if you had heat before
the trans was put in! I think there's a vacuum reservoir underneath
the car, passenger side, up front...it's a plastic reservoir, should have
a line leading to engine and one leading to passenger compartment.
Check for vacuum at the engine line and at the line leading to the passenger
compartment. Fix as necessary. You might try putting straight engine vacuum
or vacuum pump to line going to passenger compartment (there are check
valves somewhere too, it IS a turbo engine!) and see if that actuates the
heater valve/flappers. The actual vacuum switch is pretty reliable,
but I've had to replace the climate controller/computer on my 87 764T.
Climate Control Instability. [Query] Recently I have noticed
that my climate control has a new personality; in fact, several of them.
Our early Spring days in Charlotte sometimes require heat, and sometimes
a/c. My trouble is that the hvac system delivers heat, then coolness, then
nothing, then more unpredictability. This happens when set to a temp or
total heat or total cool. What's more, the system's ability to select the
right venting for defrost, heat, a/c, etc. has also gone mad. Anyone
had this problem, or recognize the symptoms? [Response: Abe Crombie]
The manual on this version ECC contains no troubleshooting charts. It only
has the list of fault codes. The fault code list contains no fault tracing
either. Any fault codes that would impact temp regulation would make the
A/C button flash on start up and this was not mentioned.
Does it not provide heat if you go to
absolute last stop HOT and cold air if you go to the absolute last stop
COLD? These end points override the temp sensors. The temp knob being
set to either full end point should make system default to the respective
mode. If this isn't happening then the servo that moves temp door needs
inspection. If the temp goes to the proper mode at end points but not in
any other temp setting (normal operation as opposed to end point defaults)
then the ambient sensor next to blower in blower case would bear inspection.
Air Conditioning Sensor Not Operating. [Query:] When its cold
out, usually around 50 degrees, the air conditioning works OK. When its
warm out, it doesn't work at all. No fan, No a.c. I assume its one
of the sensors, probably the one on the dash. Its a 3 wire affair with
a small lens in front. The other one is in the ceiling light, but I don't
think that's the one giving me a problem. Any suggestions?
[Response: Abe Crombie] The solar sensor is not going to cause anything
to fail to function on that system. It only makes the system go slightly
colder when it's sunny. It sends no signal anytime it's dark outside.
The sensor next to blower motor may be at fault. Turn the air dist knob
to face vent, the temp to full cold, fan in AUT, a/c switch off, and recirc
on. Now punch the a/c switch on and then off and count the flash code,
punch a/c switch again and repeat reading two more times. This will give
any fault codes that are present in system. The sensor can be bad and give
no code as the system doesn't know it is defective as long as it gives
a reading that is within -50F to 180F. If it says it is 60 deg out when
it is 96 the control unit doesn't know it is a bad reading.
Climate Unit Diagnostic Codes. The ECC climate unit in air conditioning-equipped
cars can detect certain system faults and display the appropriate diagnostic
trouble code by flashing the lamp in the A/C button. If the control
module detects one or more faults, the driver is warned by the flashing
A/C button. If a fault is major, the lamp will flash continuously
while the engine is running; if minor, the lamp will flash for 20 seconds
after the engine is started. To read the diagnostic trouble codes,
the engine must be running; the blower selector in AUTO setting; the function
selector in VENT setting; the temperature switch set to maximum cooling;
the recirculation switch pressed in; and the A/C switch released (out).
Shine a strong light on the solar sensor in the dash speaker; otherwise,
the DTC for the sensor will be displayed even if fault-free. Retrieve
the DTCs by pressing the A/C button in and releasing it within 5 seconds.
If several DTCs are stored, they will be displayed sequentially.
All will be erased when the ignition is turned off. If no faults
are set, then "1-1-1" will be displayed. Note that faults may be
in the component or in its wiring.
To diagnose cars with ECC but without air
conditioning, no trouble light will illlumine; the system will fail.
Remove the ECC module from the dash panel, take off the cover plate and
press the diagnostic test button twice within 5 seconds. Read the
DTCs from the nearby LED lamp, pressing the button after each DTC to read
any more codes.
Table of ECC Diagnostic Trouble Codes.
[Fault Classes: A: Serious; M: Minor;
I: No warning to driver]
temperature sensor (on blower housing):
circuit or short-circuit to 12V
temperature sensor (in roof light):
circuit or short-circuit to 12V
temperature sensor (in heater):
|| Open circuit or
short-circuit to 12V
|| D+ signal level
||Solar sensor (in speaker
|| (Note: illuminate
this with a lamp to clear code)
|| Open circuit or
short-circuit to ground
|| Short-circuit to
|| Pin 17 or 18 connected
incorrectly to 12V
|| Motor activated
for too long > 10 seconds
|| (blocked motor
or failure of motor supply)
||ECC Control Panel:
|| Faulty temperature
|| Starting current
too high, motor seizes or
|| turns sluggishly
||Power terminal incorrectly
|| 12 V for the solenoids
relay (cars with air conditioning)
cooling fan relay (cars without a/c)
FAQ for 7xx/9xx/90 Cars
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