Hello Everyone, I have a 1996 850 Turbo Wagon 177K and had the AC working great for several years on one charge. This year the clutch was not engaging, so first I tried to add R134 with a gauge and got a reading of about 100 psi and still no clutch engagement. Next I bridged the low pressure switch and the clutch engages fine which causes the pressure to drop to 35. I added some R134 from a new can and the pressures are 45-50 when I force the clutch to engage by bridging with a wire, and around 100 when I remove the wire and the clutch dis-engages. The pressure is spot on according to the specs and it blows cold air just fine when I force the clutch to engage using a wire at the low pressure switch. So the big question is, have I likely isolated the problem to the low pressure switch ? if it would simply close and open from time to time I think I would have air because that's what I'm simulating with the wire. Nothing other than the wire bridge will get the clutch moving. Thanks for any help. Arlo

 

So you have a bad switch or are low on the charge. Do you know anyone else that might let you try theirs in your car for a sec?

 

No, but I really tried to get a lot of R134 in there and last time, several years ago, the clutch kicked in after I only added a little R134. This time I'm between 45-50psi at the lowest and not once does the clutch kick in on it's own. I have a u-pull-it close enough which always has a few 850s so I may try to get a switch or 2 there.

 

Check the switch with a continuity tester, but you likely have a bad switch. I HAVE, however, seen the voltage drop from the switch be enough to keep the clutch from engaging when the air gap between the clutch and the pulley is too large- a common issue on Volvos. Search "A/C compressor shimming" for details. The voltage drop across the switch causing this is quite rare, but it does happen. Also, that switch is going to be the same on any 93-98 Volvo.

 

It was the switch, got 2 at the j yard and I'm all cold now. Thank You for your help. Arlo