Electrical diagram answer

[smvorndran]

My nephew's Equinox AC compressor is not kicking on. I'm leaning towards the AC pressure switch. It has 3 wires instead of 2, so I'm having trouble figuring out which two wires to jumper to check to see if it's the switch. It has a full charge, it just won't kick on. Can somebody tell me which wires I need to jump?

[tri again]

FULL charge?

just filled?
Maybe the pressure is too high and really nothing to fool with.

What kinda of vehicle?

If it simply will not kick on, I'd check fuses, relay etc.

PCM? maybe it's a ford?

There are sites just like this for other vehicles.
I use ford-trucks.com

That pressure switch may be keeping it from coming on because the pressure is too high.

I would think that if an overpressure switch didn't work, or failed, it would work
even if the pressure was too high.

Man o man, I'd definitely get some better info before a hose blew
and ruined something really important, like your vision.

safety first

[twitch101]

Both right i guess black and grey.

[smvorndran]

A shop checked it out and told him it had a weak compressor, but the freon charge was fine. He's a smart kid, but dumb about cars. The guy wants to sell him a new compressor and purge & charge the system for $1100+. I told him it would be worth changing the $35 sensor before dropping $1100 into a 2005 Equinox. I've had that sensor go bad on my vehicle before. He's in South Carolina, so I can't just go over and check it out for him. He just moved to the area, so he doesn't know if it's a reputable shop or not.

[Mosh]

Jumpering those wires will not work.

When the system has low pressure, the PCM will disable the compressor relay. So if you jumper the wires the PCM will percieve that the system is empty.

When the system has high pressure, the voltage feedback would be 5 volts, as if the sensor was unplugged and the PCM will think there is too much pressure and disable the compressor as well.

If you measure the middle wire with key on engine off with a dvom,( DVOM positive to the middle wire and DVOM negative to a good ground) you should have somewhere between 1 volt - 3.5 volts. If so then the switch is good and the system has good pressure.

Really a scan tool is needed. You need to see if ther PCM is seeing a request from the AC control head.
Try grounding the (C1 33) wire with a test light or jumper wire and see if the clutch kicks in with the car running.

There is also a sensor in the evap core that disables the clutch if the evap core starts to get too cold.

[twitch101]

not for 1100! compressor is easy to change and you can loan the tools from autozone. find him a simple tutorial online and a little basic refrigeration.

[JayBone]

try to youtube the issue. tons of video on how to do stuff.

That's what i do anyway.

[Ironbnder]

not for 1100! compressor is easy to change and you can loan the tools from autozone. find him a simple tutorial online and a little basic refrigeration.
That compressor probably list for over $700 so for $1,100 turn key job is not bad, figuring he is changing the filter/dryer and flushing the system as well. The warranty would be this selling point on this one. If you do it yourself and burn up the new compressor and go crying back to Autozone they most likely will not warranty it, plus you are out the cost of freon and rental of a vacumm pump. Then when you take it to a real shop they are going to re-change the filter/dryer, reflush the system and still charge you $1,100.

Unless you are comfortable working on auto A/C units, the parts are to expensive to learn with.

[twitch101]

im not familar with the cost of new parts. my 96 chevy is cheap to work on. plus im an ac tech so maybe it seems like a little job to me. check cost at rockauto.com

[tri again]

s.n.- With the old R12 systems we used to evacuate
(vacuum pump) them for Hours, like 4 or 5 hours to explode any moisture.
A procedure not to be skimped on.

Might be different now with the 'new' systems but water is water and turns to vapor under a vacuum.

as in...water will 'boil' at room temperature under a vac.

Pretty sure I've forgotten more than I ever knew so just be careful and wear safety goggles.