My 95' 850 TURBO will stop to run A/C while weather is too hot ( > 35 centigrade) , but at normal time , A/C run very well ( somethings I even
consider its performance is better than normal car ), too cool for me.

When A/C is stop , the clutch of compressor is not activate , after about one minutes , the clutch activate and compressor start , but after seconds it stop again .

I just turn off A/C and wait for about ten minutes , and turn on , everything is ok .

And I have notice the compressor is usually just activate about 10 seconds and stop by release clutch of compressor for a while , then compressor start again .
I consider the frequency of activate and de-activate of compressor clutch is too high , but I don't know it's normal or abnormal .

I guess there might something wrong of my A/C , maybe pressure of compressor is too high then disabled by high-pressure switch of A/C.

Any idea ?

Now that I think about it I used cryo-seal which informs you that you must chnage the H valve/Orfice tube. I never changed that, do you think that could be the problem and not the clutch of the compressor? BTW can someone tell me where the Orfice tube is?

This is a common problem. You have a faulty high temperature cutout switch in your compressor. This switch was designed to turn off the compressor if it overheated. This switch can't be replaced (I was told)and you must replace your compressor @ $800+. I have a 1999 S70 and this condition has gotten worse. This "cutout" for 5 minutes would only occure when the outside temperature was over 90 degrees F. That only occured a couple days a year here in Cleveland. Thinking back I know my A/C cut out when the car was new however it never happened very often so I forgot about it. I read somewhere that Volvo techs in warm climate countries have found a way to disable the high temperature switch in the compressor. I am going to experiment this week by releasing some regrigerant from the system and refilling it with an R-134 Oil Charge to see if the additional lubricant makes the compressor run cooler.

Why don't you add some Diet Coke the system while you are at it. I heard from a mechanic that it does wonders to HVAC systems.

Mike, I'm sure you are a nice guy, but . . .

intentional venting of refrigerants in not only illegal, but more importantly, it is wrong.

Adding more oil will not make your compressor run cooler.

You just said that the temperature sensor/switch is faulty. Why are you then concluding that the compressor is therefore running hot? If you know a "thermometer" is faulty, why are you then relying on that "thermometer" to make a critical judgement?

Although I have not played with this sensor/switch, from a picture I have of it, it is external to the compressor and is, therefore, easily bypassed.

I think, however, you have another problem. I don't think the switch is faulty at all. I think you system is low on refrigerant so what refrigerant is left is picking up too much heat in the evaporator and superheating to the point it is overheating your compressor.

But don't just go willy-nilly adding refrigerant. Bring the car to another shop and have an HVAC expert examine your system.

Hi,

I think I have the same problem (mine cuts out when i'm stuck in traffic or driving slowly)... where exactly is this overheating switch... i can't find it in my Haynes.

TIA,

Bass850
Dark blue 1994 T5

Froma drawing I saw on AllData, it is located midway along the length of the "cylinder" which forms the compressor.

Although in the drawing, it looks very accessible, I'm sure, from the way everyone is saying how it is "not repairable," that it is located in an inaccessible location when the compressor is mounted on the engine.

But, at least from the drawing I am looking at, the switch is external with two wires going to it. I assume that this switch is probably normally-closed so bypassing the switch should be a piece of cake.

I've never taken off the compressor, which may be a bear, and the reason why shops are saying that you just replace the compressor. The thermostatic switch may also not be available as a separate part.

BUT THE MESSAGE TO EVERYONE IS: IF YOU HAVEN'T SPENT A LOT OF TIME LEARNING ABOUT HVAC SYSTEMS, LEARNING WHAT YOU CAN DO, AND WHAT YOU CAN'T DO, DON'T SCREW AROUND AND START EXPERIMENTING. MUCH OF WHAT YOU WILL BE DOING IS ILLEGAL AND WRONG.

It may NOT be the overheat switch, it probably is insufficient refrigerant.

Go see a competent HVAC technician, because your inexpert uneducated guesses will eventually cost you a new compressor anyway.

I do wonder if it is not sufficient refrigerant , why the performance of
my current A/C system very good ( it's produce very cool air ) ?

How can I ensure there is a high pressure switch in my car ?

First of all I did take my car to a shop that specializes in HVAC. They checked out the A/C and found that it did not need refrigerant and was operating fine until for no reason the compressor shut down. They felt it was a bad sensor or ECU and suggested that I take it to a Volvo dealer to be checked out. I then took my car to a Volvo dealer in Cleveland and had a Volvo Master Technician check it out. He is the one that told me that the high temperature cutoff switch which is located inside the compressor is the problem. This switch or circut breaker is similar to the bimetal fuse used in hair dryers. Heat warps the bimetal strip to open the circuit. When it cools down it flattens the bimetal strip and makes contact to complete the circuit. These switches are only a last resort and intendend to protect your compressor if the low pressure switch does not shut down the compressor if you lose refrigenant. There is a good chance that the switch was set too low from day one and would have been replaced under warranty if I lived in a warm weather climate and the problem would have showed up earlier. All the external switches checked out and when the compressor cut off he told me that there was still power going into the A/C. He added that my compressor was not overheating however because of the high ambiant temperature it reached a temperature above the sensor setting. As far as me replacing some refrigerant with some oil charged refrigerant, since when has R-134 been considered harmful to the environment? Since my A/C is now starting to cut off at a lower ambiant temperature (85*) my guess is that either the high temperature cut off switch is getting worse or there is more friction causing more heat to build up in my compressor. Doesn't oil reduce friction thus reducing operation temperature? What do I have to lose? If it doesn't work I will have to replace the compressor anyway.

I have the same problem and the dealer said I need a new A/C compressor. Both the low and high pressure sensors have been replaced. The board told me to take the thermo sensor out of the A/C compressor loop. I unplugged the appropiate electrical wires and over road the sensor. I still had the problem and the dealer told me after testing that they noticed the A/C compressor cut out and checked to see if power was going to the compressor and they said yes. That lead them to believe it's the clutch, which is one assebly with the A/C compressor. Does this sound right? Do the clutches go bad often? Do I need a new compressor?

Thanx Sandro

"since when has R-134 been considered harmful to the environment?"

SINCE ALWAYS!!!

R-134a is "better" than what it replaced, R-12, but it is still harmfull.

Refrigerants are harmful in two major ways:

1) Ozone Depletion Potential (ODP)
2) Global Warming Potential (GWP)

R-12 was bad on both ODP and GWP. R-134a is great on ODP (because it does not contain any chlorine), but it is still bad on GWP.

To quote from EPA regulations:

"Under section 608 of the Clean Air Act, it has been illegal since November 15, 1995, to knowingly vent substitutes for CFC and HCFC refrigerants during the maintenance, service, repair and disposal of air-conditioning and refrigeration equipment."

R-134a is one of these substitutes.

You may be asking, well than, how come I can buy this stuff at the local discount store. Well, this is because the EPA has not yet been able to muster a prohibition on the sale of R-134a. It is still illegal to "release" R-134a, it is just not illegal to buy R-134a.

This is one of those stupid government rules where it might be legal to possess something, but not to sell it (actually, the reverse logic).

Here is a link to some information on refrigerant substitutes.

http://www.ucsusa.org/environment/ozone.faq.html (look at paragraph 6)

But the bottom line is that it is illegal, AND MORE IMPORTANTLY, WRONG, to vent R-134a, BECAUSE IT IS HARMFUL TO THE ENVIRONMENT.