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post #13 of (permalink) Old 05-15-2011, 04:31 AM
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Join Date: Jul 2005
Location: Delray Beach FL
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Originally Posted by hifiandmtb View Post
My a/c has just stopped functioning. Here are my symptoms:
1. The a/c momentary switch light comes on.
2. The compressor doesn't cut in. No cool air from vents.
3. All three fan speeds work fine.
4. The recirculation light comes on (which I think means the switch pack's ok).
5. Fuses F7, F19 & C4 are fine.
6. The connectors into the relay pack on the LHS wheelarch lining are secure.
7. The circuits inside the relay pack on the LHS wheelarch lining look fine (popped it apart to check).
8. I have 12v into F19.
9. I fail to see any voltage into C4 w/ the key in the ignition & turned to position II (didn't try with the engine running, though) - may need to double-check this.
10. The a/c was working fine before I wired up my oil temp gauge which takes power from C2 (piggy-back) - and yes, my wipers still work!
11. Even with the oil temp gauge completely unplugged, still no a/c compressor action.

As I'm a big "what did you touch before it went bang?" kinda guy, how can I be sure what I've fiddled with hasn't caused the a/c issue. I'm also an advocate of something unrelated going bang under coincidental circumstances ;-) I really wish there was a way to diagnose the a/c no worky cause (i.e. low gas) without having to check the gas level!

Also, should the radiator fans come on at half-speed when the a/c is turned on? My rad fans *don't* come on when the a/c button's pressed (and the light's lit) but I'm assuming that the fans are driven by the compressor cutting in & *not* the button pressed.
There is only 12V at C4 when the compressor relay closes, which is controlled by the ECU. Try jumping the relay contact by bridging brown/white wire to the red at the AC control module to see if the compressor starts.
If it does, it could be the Trinary switch not signalling the ECU to start the compressor due to low refrigerant level or defective wiring or switch.
The fans are also controlled by the ECU and run at half speed if the compressor is running.

Last edited by SirLotus; 05-15-2011 at 04:39 AM.
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