I know this has been on here a number of times (I found this place last summer when this first happened) but I am not sure I ever jotted down the best advice.

I have a 1997 V90 with 115k on it. It runs great and I am very happy with it. The issue is the AC. On hot days it will work for a while (always starts off fine) then will cut out for 1-5 minutes then will come back on for a similar (sometimes longer) perdiod. This cycle repeats over and over. I think this is no uncommon on this model. I have found a local shop (primarily a Benz shop, but do a lot with Volvo) that I have developed some trust in. I am not sure if they have seen enough of these to know what is going on - but I think if I had an idea I could help them help me. I am not overly hands on, so I need help.

Anyone have the solution (or possible solutions) to this common problem?

Greg

Well, you are going to have to visit the shop when it is not working, or grab a test light yourself. When it isn't working, see if you have power to the low side pressure switch. If you have no power to the low side pressure switch one of two things has happened. Either the controller, all by itself, has decided not to send the signal, or the high pressure switch (the purple one on the condensor) or the engine coolant temp sensor has told the ECU to disallow the compressor. This happens when the pressures get too high or the engine gets too hot. Sometimes this is really caused by a too high system pressure because the two stage fan doesn't bump up to the second stage (faulty relay or faulty brown switch on the condensor), sometimes this is caused by a faulty purple switch saying that the pressures are too high when they are not, and sometimes it is caused by a faulty engine coolant temp sensor, saying that the engine is to hot when it is not. Usually, if it is the ECT, you will have a check engine light on.

Next...if you have power to the low side pressure switch, jump the switch, does the compressor come on? If the compressor comes on, the problem is the low side pressure switch. If the compressor doesn't come on, it's the compressor clutch. I usually replace the compressor though...I've had really bad luck replacing just the clutch...usually the compressor fails within the year and I'm blessed with an angry customer.

Hope this helps,
Chris

Thanks a ton for all this info, although much of it is above my head. The check engine light has just come on recently, so I am wondering if that is related to what you said.

Greg

I'll be glad to explain anything, I talk the same way I type, too fast. I've had many customers tell me that. I keep trying to slow down, there is just too much on my plate to do so. Something might not get done.

Is the light on the ECC flashing...you know the little lights at the recirc and snowflake buttons? I think you can read these yourself. I know that my diagnostic tool (straight from Volvo) doesn't read the climate codes in a 97 960, I read them manually at the ECC...suspect yours is the same.

The check engine light will have to be read at a shop.

Chris

Ok, I took my car into the shop I use. This was for the check engine light and a brake issue I was having (making a leaking air noise). Turns out the brake thing was causing the check engine light thing. I have a bad brake booster that was causing a vacuum leak or something like that. The check engine codes were Air Intake and fuel rich/fuel lean. The guys thought that the brake booster issue was likely causing that. They replaced the booster and then reset the codes. they then drove it and check the codes agian - nothing.

I wanted to deal with this problem first, as it was effecting my braking. I will address the AC next. Could there be chance that this issue was related to the AC issue?

Thanks
Greg

Hey!
I have the similar problem with my former 850. I have replaced the AC compressor clutch and problem eliminated...

Regards,
Oleg

Other possibilities are the high pressue cut-off and the high compressor temp cut-off.

DEWFPO

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1998 S90 068,300 and 1995 964 152,300

If the on corresponds to lite engine loading, and the off corresponds to heavier loads like during acceleration or climbing hills the cause is the "dual acting" vacuum motor that controls the "mixer" door inside the heater/AC unit. The side that has the actuating shaft running through it develops a leak and it can't hold it in the cold air position if the vacuum goes away.

The only solution is replacement. Unfortunately it is buried inside the dash and is a fair amount of work to get to in order to replace it.

If you search the FAQ's you will find a "short cut" method but it requires skill and luck and I choose the factory manual method for doing mine. Took me about 8 hours as a DIY.
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'96 965 with 16' wheels at 114K. Had '85 745 Turbo Diesel for 200K.

My ex-S90 exhibited the same symptoms, the first time in Yuma AZ in August. It behaved for a bit after that incident but got progressively worse. The controller was the problem, an expensive fix. Since the car had so many other problems, rather than pay yet another repair bill, I traded the car for something more reliable. The local dealer tried to troubleshoot the problem by replacing parts one at a time (professional,eh?) but I called a halt to that and took it to an independent Volvo mechanic.He put a known good controller in the car and all was well. I paid him for his time, gave him his good controller back and got rid of the car. Too bad, I really liked the car when it wasn't in the shop.
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Roy Olson