94 a/c problem
Thread Starter
Intermediate
Joined: Aug 2019
Posts: 27
Likes: 3
94 a/c problem
My 94 a/c doesn't work. It has no fault codes and every thing works except no cold air. The compressor doesn't run but the radiator fan does. It has a full 134 Charge. I tried jumping the low pressure cut off switch to no avail. I am leaning towards a bad pressure sensor for the ECM. It has a good ground but I didn't find any 5 volt ref voltage. If a replacement sensor doesn't work and I indeed have no ref voltage can I pick it up elsewhere on the ECM? Any help would be appreciated.
Thanks
Dave
Thanks
Dave
Safety Car
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
Do you get 12 v. at the low pressure switch when you attempt to activate the a/c?
If you put 12 v. to the compressor clutch connector, does it operate (engine not running)?
Does the compressor clutch have a good ground?
If you put 12 v. to the compressor clutch connector, does it operate (engine not running)?
Does the compressor clutch have a good ground?
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,561
Likes: 4,030
From: Cape Coral, Florida
Yes, try jumping the load side of the AC relay (pins 87 and 30) and see if the clutch engages...looking at the wiring it looks like the 5 volt ref. is shared with the MAP sensor...do you have 5 volts at the MAP ??...if you do you may just have an open in that gray wire somewhere between the sensor connector and where it splices into the MAP. Now you checked for the 5 volts with the sensor UNPLUGGED ??...now with the sensor plugged in if you back probe the 5 volt ref. you should not have 5 volts nor 0 volts !!...on my C5 that sensor tells the PCM what the AC line pressure is...not less than 30 psi or more than 430 I believe !!...get yourself a piercing probe and start working your way back to the PCM until you see the 5 volts again.
Last edited by C5 Diag; Aug 30, 2019 at 05:29 PM.
Thread Starter
Intermediate
Joined: Aug 2019
Posts: 27
Likes: 3
Ok I will dig a little deeper. Thanks for the suggestions, Car runs fine so Mass Air flow must have ref voltage. Need to do some stuff with the wife so I probably won't get to t it until later on today
Dave
Dave
