740 air conditioner compressor won't run

cityfarmer · Post by **cityfarmer** » 29 Apr 2006, 11:18

My daughter's 1991 740 air conditioner compress will not come on. Fuses are fine. We ran a ground shot to the compressor and got it to turn 1 time. The compressor seems fine as does the clutch. A recent trip to an independent Volvo shop turned up nothing. They give up. Can someone provide help on this? Is there a way to wire it directly and bypass the wiring loom?

petershen1984 · Post by **petershen1984** » 30 Apr 2006, 20:44

Hi, you never mentioned whether you checked the coolant levels. The 740 compressor has a pressure sensor that prevents "dry running" when the coolant has leaked out to a low level. If you bypass this safety measure you'll destroy the compressor real soon.

Now, if you do have cooling, and the compressor worked when you connected it to a different "ground," then it's time to check electrical relays from behind the control panel -- if these fail then the unit is not sending the current needed to trigger the operation of the air conditioning...

cityfarmer · Post by **cityfarmer** » 01 May 2006, 11:21

Thanks for the response. I forgot to mention that the independent shop that checked it out said they had tried a new climate control unit and that the coolant charge was good and so was the a/c relay. They gave up

Peter Coutts · Post by **Peter Coutts** » 04 May 2006, 21:03

I have the same problem. My compressor is only two years old and was working fine... I suspect a relay. Where is the a/c relay located that triggers the compressor?

Thanks Peter