95 GT AC not working

aj351w · Jun 25, 2023

Help please. When we bought the 95 GT for my son the AC didn't work but figured it would be an easy fix as there was a leak and no freon in the system. First I replaced all the o-rings then did a leak check and it failed so I just got out the shotgun and bought a new condenser, compressor, and filter/dryer. Did a leak check and all is good. Started charging the system and the compressor never kicked on. Checked Low pressure switch and high pressure switch, both are functioning properly. Checked the wiring for continuity between switches to CCRM, and from CCRM to compressor clutch, all good. Checked for voltage when AC is turned on and it makes it through both switches to pin 21 at the CCRM, but nothing coming out on pin 23. Also verified the clutch works on the new compressor by applying 12v. Swapped a known good CCRM from my 95 Cobra still no AC. The only input to the CCRM that can disable the AC is the WOT (pink/yellow wire on pin 22), don't know exactly how to test that though and if the car thinks it's at wide open throttle all the time it would probably like crap.

Other information that might play a role in this: It's a Cobra swap so J4J1 computer and 24lbs. injectors, as far as I know all the wiring is the same so that shouldn't matter. Also one of the fan speeds doesn't work, this is verified with a KOEO test (code 564 Electro Drive Fan Circuit Fault). I think it's the low speed, which I believe is supposed to kick on when the AC is commanded on. Would a not working fan cause the AC to not turn on? I guess I could try swapping the fan from my Cobra, just getting tired of shotgun maintenance. Any ideas?

Slice · Jun 27, 2023

You might be on the right track. I had an old Chevy car early '90s and it had the same problem not all the fan speeds would work. Turned out it was a little electronic thing that goes under the dashboard near the switch. It literally looked like four different little coils each one with different amount of spirals to give varying levels of resistance I guess. I'm talking like maybe only five or six Spirals and then the next one seven or eight spirals. Anyway before you change the fan find out if there is something similar for our old mustangs. It might be that part. Has I recall it was a pretty cheap part to buy.

07GtS197 · Jun 27, 2023

You’ll have to jump the low side switch to get the compressor to turn on while filling since it’s empty.

aj351w · Jun 29, 2023

07GtS197 said:
You’ll have to jump the low side switch to get the compressor to turn on while filling since it’s empty.

The first bottle pressurizes the system enough to activate the low pressure switch, I verified with gauges and multimeter.

07GtS197 · Jun 29, 2023

aj351w said:
The first bottle pressurizes the system enough to activate the low pressure switch, I verified with gauges and multimeter.

You said the compressor never turned on though.

aj351w · Jun 29, 2023

07GtS197 said:
You said the compressor never turned on though.

Correct, the 12v signal goes to the CCRM, but doesn’t make it out to the compressor.

maillemaker · Jun 29, 2023

I just spent $1200 on a new compressor being replaced, only to find out the actual problem was the CCRM, which they replaced for another $400.

aj351w · Jun 29, 2023

maillemaker said:
I just spent $1200 on a new compressor being replaced, only to find out the actual problem was the CCRM, which they replaced for another $400.

Yeah I was hoping it was the CCRM, I have a spare, also have a known good one in my 95 Cobra, tried them both, still no 12v out of the CCRM. I’m going out to change the fan motor now and will check all the pins and wiring again…

aj351w · Jul 2, 2023

Finally got it working, first I found out the fan in there was a crappy aftermarket single speed so I found a used OEM 2 speed fan. Put that in hoping the AC would start working now that I no longer have code 564 Electro Drive Fan Circuit Fault and low speed now works which turns on when the AC is turned on. Well still no AC and the fan didn’t turn on when I turned on the AC. Grasping at straws I tried my other CCRM again (same one I already tried before and didn’t work). This time the low speed fan kicked on and the clutch engaged. Don’t know if it was the combination of a bad fan and CCRM or just playing with the connectors and wiring harness jiggled something just right and is now making contact. Either way I’m happy and have cold AC.

07GtS197 · Jul 2, 2023

Hmm I’m wondering if the ecu thinking the fan wasn’t turning on disabled the ac. Glad you got it figured out.

Slice · Jul 3, 2023

aj351w said:
Finally got it working, first I found out the fan in there was a crappy aftermarket single speed so I found a used OEM 2 speed fan. Put that in hoping the AC would start working now that I no longer have code 564 Electro Drive Fan Circuit Fault and low speed now works which turns on when the AC is turned on. Well still no AC and the fan didn’t turn on when I turned on the AC. Grasping at straws I tried my other CCRM again (same one I already tried before and didn’t work). This time the low speed fan kicked on and the clutch engaged. Don’t know if it was the combination of a bad fan and CCRM or just playing with the connectors and wiring harness jiggled something just right and is now making contact. Either way I’m happy and have cold AC.

Geeze so the average smuck with average wrenching skills would probably fail at this fix!