Engine Size: 3.5L
Refrigerant Type: OEM
Ambient Temp: 75
Country of Origin: United States
Hello all. Haven't done a lot with AC units because I don't really understand them. A few weeks ago the AC unit in our van was acting funny. It would kick in and out when it should have been on. Now it's out all together. Some of the things I've checked.....
The compressor plate is not spinning so the clutch isn't engaging.
I've swapped around the relays with no luck, so it's not the relay.
I tried charging the system, but with the compressor not on, the pressure is too high and no refrigerant goes into the system.
I fix most things on my car because I try to avoid taking it to shops, too expensive. Plus I like to learn new things. But I don't know where else to go here. I know it could simply be the compressor, but I want to change that as a last resort. Are there other items I can rule out before a compressor change? Any help would be appreciated.
Check if voltage is reaching the compressor clutch. If it is you may just have a clutch gap issue. If it is not there is an electrical problem with the controls.
To extend what Cussboy said, all cars have a protective mechanism of some sort to prevent the compressor from running if the pressure is abnormally low. So checking with gauges is important in a "compressor won't start at all" situation, but you don't try to charge. Pressure of zero would mean there's a big leak.
Thanks for the information. Where do I check for the voltage? Can I just check at the solenoid or do I have to check on the compressor itself? It will be quite a treat if I have to try to get to the compressor itself. And if I can do it on the solenoid, how do I do that?
Edited: Sun September 27, 2015 at 1:39 PM by Jfoerch
You can check for power at the clutch relay. Start the car, turn on the A/C. Pull the relay out of the socket. Did it click? Not sure? plug it back in & listen carefully.
If it clicks, the system is commanding a compressor start. At that point you need to access the clutch & it's connector. On that car it is done from below, wheels cranked to the right, R/F wheel removed. Pull the inner fender plastic.
You can check the coil with an ohmmeter or test light. the Clutch gap should be re-set if the coil checks ok.
If you check the owner group forums you will see that 2007 was a transitional year for that engine / vehicle combo. Some owners had compressor clutch coils fail. More than one compressor was used. I believe even the belt tensioner changed mid-year.
"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
Ok... So I checked the relay again and it does click. Now I'm working under the car. I've got the plastic fender and wheel removed. I've knocked on the compressor plate with a wood stick and it didn't start spinning. I can spin it by hand, but I don't know how much resistance is too much. Now I'm trying to figure out how to check the ohms on the coil. The plug seems to be tucked up and away and super awesome for accessing, but I guess that's the next step. Any other tips would be great. Thanks so much for the help already.
I test the ohms, and amps at the a/c relay terminal- unplug the relay- figure out the terminal that leads to compressor coil, then do an ohm to ground- should be about 3.50 ohms resistance on a good coil, a bad coil will read 1 if shorted, or wide open (overload) if open circuit. You can also feed it 12v from the battery (at the relay terminal) and do your amp checks- o amps means coil is wide open, a good coil should read about 3-4 amps draw- shorted coil will read greater than 4 amps...
All this is done without unplugging the compressor coil- this is the preferred method, since getting access to the coil plug on compressor can often be a real pain-
Do keep in mind that before you condemn the coil, that you check the compressor plug and wires to the coil for bare wires or chaffed or frayed, or broken wires.
Also test the power coming to the relay, to be sure your a/c fuse is not blown- usually must be done with ignition on- but sometimes is battery hot.
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......
GM Tech, I would ask why I never thought of checking coils from the relay, but I know I'm not as smart as you. This will save me a lot of time! Thanks for the tip!
I bought a can of 134a at w**-mart that had a stop leak, oil, and dye in it. It also had a hose and a gauge, so now I'm an AC pro!
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