1996 Volvo 850 Turbo with A/C problem

Okay it doesn't appear that my a/c is losing refrigerant. As best as I
can diagnose the problem here is what I have come up with:

When I start my car the A/C comes on and some times it will stay on
for hours. Other times it will only stay on for 10 minutes. When I
turn the a/c off 10 minutes and then back on it will work fine. But
at some point it may go off again. The vent continues to blow but it
feels like it is burning outside air. The air is no way cold. When I
press the a/c off/auto switch I can hear the engine idle differently
which indicates the compressor is kicking on and off but only hot air
comes out of the vents.

I am not sure if it is a compressor going bad; a loose wire somewhere
or what?

Help!!! It is 90 degrees here. I don't have the money to take it to
Volvo. I was thinking of letting this independent mechanic take a
look at it.

Thanks

DJ

 

Can you see whether the compressor clutch is kicking in? It could simply be
low on refrigerant, you may want to take it to an AC shop, definitely don't
go to the dealer, the car is too old for that to make sense, they're only
really good for fairly new cars that are under warranty.

 

--

About 2 years ago my '96 850 definitely had evaporater leaks and I had it
replaced.

A couple of months later I had the "pressostat" switch fail. This happened
when it got hot. It's located just above the exhaust manifold on the low
pressure refrigerant return line, on the fire wall. The return refrigerant
keeps it cool when it's running. When I stopped the car, even for 5
minutes, it would heat up from the exhaust, and the a/c no longer work when
the car was re-started. It is mounted on a "schrader" valve and there is no
need to de-gas and recharge if you replace it.

A couple of months after that I had the compressor "overload" switch fail.
Cooling suddenly ceased. This switch is mounted on the compressor itself
and can be bypassed by simply by changing the plug and sockets around.
Access is quite tight, for my hands anyway. Note the overload switch is not
the diode mounted on top of the compressor, but is fitted in series with the
compress clutch wire. From what I've read the overload switch fails quite
regularly and is not used on later Volvos. I have run without it since then
and have had no further problems.

From your fault description, I'd try bypassing the overload switch first.

But if you have both problems, you will find the symptoms very confusing.

regards
Barry

 

Okay it doesn't appear that my a/c is losing refrigerant. As best as I

Start by checking if the compressor goes on and off for real or it only
feels like it, easy to see by looking at it.
If you have problems when its real hot i would guess it could be the clutch
distance thats to big. You can measure the distance between the clutch and
the wheel with a feeler gauge.

Greetings Niels

 

When you say check if the compressor goes on and off, do you mean it
should go on and off in a cycle or should it stay on as long as the A/C
is turned on ?

 

Start by checking if the compressor goes on and off for real or it

I mean check whether the clutch engage when it feels like it or it fails
because of to big clutch distance.
Normal operation is it cycles on and off.

Greetings Niels

 

thanks, then my clutch is OK - but I think I need my A/C serviced since
the air coming from the ducts doesn't feel very cold.

 

That sounds right to me - some leakage is normal over ten years.

I've learned not to mess with R134a myself and only recently learned why it
has kicked my butt in previous attempts. I always recommend professionals
for that.

Mike

 

Well I am taking my car to a mechanic tomorrow. He doesn't specialize
in Volovos but I am hoping he has enough experience to troubleshoot
and fix the problem.

I don't know how to check the clutch. I know that when I first get in
the car the air blows cold. Then it seems like when I change the fan
speed it occasionally stops cold air from blowing. The vent still
blows air but it isn't cold. Then if I turn the a/c on and off I can
hear the compressor going on and off but the air doesn't get cold.
But if I turn the a/c off from around 5 mins. and then back on the air
will get cold again MOST of the time.

Before the air never seemed to get cold so I had a guy put some freon
in the car. Then it got colder as he was adding it. But I recall him
saying something about my compressor may be going bad because I guess
the guage on his device wouldn't go up to a certain number. He didn't
check the car for leaks. But the air was cold and as I drove 10 mins
from his shop the air wasn't cold anymore.

 

I can't imagine why a tech would add refrigerant to a system and not bother
to check for leaks. It sounds like either the compressor has failed, or the
refrigerant has leaked out again. Once it starts leaking it usually leaks
pretty fast.

 

I agree about the technique - not up to even minimal standards for charging
R134a. My son's system took me to school last year and I decided the stories
were true: R134a systems should be charged only by completely evacuating,
leak checking (verifying the system holds the vacuum) and filling with the
prescribed charge of R134a.

The whole story can be found at http://www.autoacforum.com/ and the details
of what it takes to charge by guage are in this part of the site
http://tinyurl.com/2gvdaa . Apparently the environmental wind tunnel can be
replaced by a whopping fan pointed at the condensor and allowing more time
for the system to settle out... looks like about 15 minutes per ounce added.
The time element - several hours of settling in the course of any meaningful
recharge - makes the weight method the only practical method.

Mike

 

Ok I took my car to a mechanic and he said he hooked it up to the
computer and the computer told him to clean the asperators. He said
that it was clogged. And he charged me $90 to clean it out and reset
the computer. He said there were no other error codes coming up.
Well the a/c worked all that day. Then two days later I was driving
with the a/c on and around 30 minutes into my trip I changed the fan
speed from AUTO to a lower speed and the air was no longer cold. I
told the a/c on and off; changed the fan speed back to AUTO but no
go. Then when I got in the car later the a/c began to work fine. I
drove for an hour and changed the fan speed and the air stayed cold
the entire time.

damn this is driving me nuts. Now I am out of $90 - not to mention
the other money I spent for the guy to add freon. The freon doesn't
seem to be leaking because I had it added over two months ago and it
still gets cold when the ac is on.

 

Barry 'baz' mentioned the notoriously troublesome over-temperature switch on
the compressor of early 850s... I think yours qualifies. The ultimate
solution is to bypass the offending switch - somebody here must have a link
to a pictorial. The switch was supposed to be protective but in reality it
was only a nuisance.

Mike

 

If someone has a link to a pictorial on how to bypass this thing,
please let me know.

Thanks everyone for all of your help. May this be the last used car
that I will ever buy.

 

Here's a brief description
http://www.brickboard.com/AWD/index.htm?id=1089111
I can't find any pictures, but it apparently isn't as hard to find as it is
to get to.

Mike

 

Mike thanks...

I found more detailed info with a photo here:
http://volvospeed.com/vs_forum/Ac-Thermal-Switch-t76833.html

Now that I feel pretty confident about what is causing the problem, I
will let someone fix the clutch gap and maybe cut the wire. I have a
very good Volvo mechanic here but he charges $85 an hour. Damn I wish
I was earning that much an hour then I could afford to hire him. I am
going to post a message on the board to try and find someone who is
more affordable.

Just want to let you guys know that I appreciate all of your help and
your research! This site is awesome!!

David

 

--

When I bypassed mine ('96 850), there was no need to cut and splice. The
existing connectors, although not identical can be plugged together to
bypass the switch. I did my over 18 months ago and no problems. But it's a
very tight spot to reach from above, like I did, just make sure everything
is cool first, so you don't burn youself. It only takes minutes to do.

regards
barry

 

Well, I just went out and connected the white connector to the brown
(or was it black) connector and the a/c came on so that is a good
thing. Now I just have to wait for another very hot day to turn the a/
c on and run it all day to see if the problem has been resolved.

David