No AC, cooling fans on
Thread Starter
Intermediate
Joined: Mar 2009
Posts: 33
Likes: 0
From: Manor Texas
No AC, cooling fans on
Searched but couldn't find anything on what happened to me yesterday. I have a C5 2001 with dual climate control. Coming home yesterday the car ext temp sensor was at 108 degrees (I'm in Texas 
. AC working fine. After a stop to get groceries, AC no longer worked. The AC light would come on, then go off. Compressor was not engaging. Belt is fine. I tried it again this morning with the same result but I noticed my engine cooling fans are staying on. (they turn off when I kill the engine). Coolant temp is reading fine on the display. (now running about 5 degrees cooler though). I pulled codes and the only possibly relevant codes are C1242 and B2262. Starting to lean toward a grounding issue. Has anyone else experienced this issue ?. Thanks...TK
. AC working fine. After a stop to get groceries, AC no longer worked. The AC light would come on, then go off. Compressor was not engaging. Belt is fine. I tried it again this morning with the same result but I noticed my engine cooling fans are staying on. (they turn off when I kill the engine). Coolant temp is reading fine on the display. (now running about 5 degrees cooler though). I pulled codes and the only possibly relevant codes are C1242 and B2262. Starting to lean toward a grounding issue. Has anyone else experienced this issue ?. Thanks...TK
Advanced
Joined: Feb 2016
Posts: 93
Likes: 8
From: Sterling Heights MI
Searched but couldn't find anything on what happened to me yesterday. I have a C5 2001 with dual climate control. Coming home yesterday the car ext temp sensor was at 108 degrees (I'm in Texas . AC working fine. After a stop to get groceries, AC no longer worked. The AC light would come on, then go off. Compressor was not engaging. Belt is fine. I tried it again this morning with the same result but I noticed my engine cooling fans are staying on. (they turn off when I kill the engine). Coolant temp is reading fine on the display. (now running about 5 degrees cooler though). I pulled codes and the only possibly relevant codes are C1242 and B2262. Starting to lean toward a grounding issue. Has anyone else experienced this issue ?. Thanks...TK
. AC working fine. After a stop to get groceries, AC no longer worked. The AC light would come on, then go off. Compressor was not engaging. Belt is fine. I tried it again this morning with the same result but I noticed my engine cooling fans are staying on. (they turn off when I kill the engine). Coolant temp is reading fine on the display. (now running about 5 degrees cooler though). I pulled codes and the only possibly relevant codes are C1242 and B2262. Starting to lean toward a grounding issue. Has anyone else experienced this issue ?. Thanks...TK
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Check the following:
Engine Compartment Fuse Box
Relays: Ignition relay #42, A/C CLU Relay 34,
Fuses: PCM Fuse, a/c FUSE #24
PCM Fuse I believe its #10 ?????
GROUNDS: Chassis Ground G-102 (just to the rear of the passengers head light assembly on top of the frame. Its for the Compressor CLUTCH ground
G-106 Passengers side of the engine, on the side of the block just above the starter. The battery ground cable attaches at the same point.
I have the schematic. Send me an e-mail address and Ill send it to you.
Engine Compartment Fuse Box
Relays: Ignition relay #42, A/C CLU Relay 34,
Fuses: PCM Fuse, a/c FUSE #24
PCM Fuse I believe its #10 ?????
GROUNDS: Chassis Ground G-102 (just to the rear of the passengers head light assembly on top of the frame. Its for the Compressor CLUTCH ground
G-106 Passengers side of the engine, on the side of the block just above the starter. The battery ground cable attaches at the same point.
I have the schematic. Send me an e-mail address and Ill send it to you.
Thread Starter
Intermediate
Joined: Mar 2009
Posts: 33
Likes: 0
From: Manor Texas
Well, I checked fuses 16, 23, and 24. All good. They are energized when running the engine (both sides). I swapped out relays 42 and 34 with like pn relays. I cleaned both multi ground connectors near the headlights. The compressor clutch is not getting voltage at the connector. Ground checks out ok at connector. The refrigerant is at +- 125 lb. I unplugged the high pressure connector with no change. Clutch not getting voltage. The fans turn on when I press the AC on switch and the light stays on for 3 seconds. Really scratching my head on this one.
Thread Starter
Intermediate
Joined: Mar 2009
Posts: 33
Likes: 0
From: Manor Texas
Just noticed I said refrigerant was 125 lb, correction it is at 125 psi .
Also, just verified that the cooling fans are on with engine running, with AC off. Cold or hot engine makes no difference. Can't help but think this is related to the AC issue.
.Also, just verified that the cooling fans are on with engine running, with AC off. Cold or hot engine makes no difference. Can't help but think this is related to the AC issue.
Advanced
Joined: Feb 2016
Posts: 93
Likes: 8
From: Sterling Heights MI
Sounds like a CTS to me, or maybe its wiring. If the fans are running with the AC off and the engine cold, then the PCM must think the engine is hot. I believe there is an overheating AC shutoff as well, which would explain that not kicking on.
I would test the CTS resistance with a cold and a hot engine.
I would test the CTS resistance with a cold and a hot engine.
Heel & Toe
Joined: Dec 2016
Posts: 20
Likes: 3
From: Pflugerville
I would try the AC right after a cold startup. If the fans come on, then the AC circuit is working, it's just the clutch not engaging. You can test for power and ground right at the clutch or at the relay at that point. If the fans don't come on, then something else is causing the AC request to be denied. Likely culprits are one of the pressure sensors or the pressures being actually wacky, perhaps from a blockage or a freon leak.
You were on the money. I work with TK and also own a C5. We unplugged the A/C pressure transducer on my car to see what the fan behavior was when unplugged on a properly functioning C5, with the A/C off. We then unplugged his transducer. When his transducer was unplugged, the fans would turn off. Plug it back in, and it would immediately kick the fans on, without the A/C running. I had a spare A/C pressure transducer leftover from an LS swap on my truck, so TK stopped by my house after work, and we swapped transducers. Everything appears to be back to normal (at least it was when he left). I'll let him chime in to confirm.
-Foamy
Last edited by foamypirate; Jul 25, 2018 at 08:02 PM.
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Thread Starter
Intermediate
Joined: Mar 2009
Posts: 33
Likes: 0
From: Manor Texas
Yes, my AC issue is no more. Part my fault for incorrectly testing the issue. When I first unplugged the pressure switch, I thought the AC was off, since the light was out, but it was actually on, so unplugging it made no difference. I just want to thank everyone for all the information and schematics. I now know how the system works and am ready for any future issues. Still have been able to fix every issue with info from this forum. Thanks again everyone...
