AC Compressor not kicking in

[Laz174]

I have a 2000 Grand Prix with the 3.1L. It is the SE1 model and doesn't have dual climate control nor the heads up display showing temprature. The problem that I am having is the the Compressor clutch will not kick in toturn on the air. I checked R-134a levels and the system was full, so I replaced the AC Pressure Sensor thinking that it was the problem from some other threads that I have read and it didn't change a thing. I checked all of the fuses and the are good, I even replaced the Relay in the Fuse block and still no cold air. I took off the outer casing to the relay and manually forced the contacts shut and then the clutch kicked on. I pulled out the relay and it isn't getting the grounding pulse that triggers it to kick on. Does anyone else know what else I can check? About the only thing that I haven't done yet is pull out the cluster to see if the switch is working, I am just taking it at face value that it is working since the light is coming on.

Any help is greatly appreciated. Just bought the car 2 days ago for my wife and she is ready to put it up for sale.

Thanks

Allan

[kustomkid54]

Could be low coolant or blowen fuse, I'd check coolant.

Good luck

[richtazz]

try jumping the two wires that plug into the low presure sensor. Even if you replaced it, you could have gotten a bad one. if the clutch kicks in with the wire jumped, then you have a bad sensor, if it still doesn't kick in, check the high pressure switch, as it would cause the compressor to not kick in also.

[Laz174]

I checked the coolant and it was up there and all fuses seem to be good. The other thing that I noticed is that the Cooling fans don't come on when the AC button is turned on. I also have a 1999 Pontiac Grand Am and when I press the AC button within 1 second both engine cooling fans pop on.

[Laz174]

Originally Posted by richtazz

try jumping the two wires that plug into the low presure sensor. Even if you replaced it, you could have gotten a bad one. if the clutch kicks in with the wire jumped, then you have a bad sensor, if it still doesn't kick in, check the high pressure switch, as it would cause the compressor to not kick in also.

Which 2 wires do I jump. My sensor is a 3 wire sensor. Red Black Gray

[AFilip5783]

Same problem with my 95 GP .In process of filling system with 134A...then take it from there..Compressor comes on when i jump the wires at the relay box,also fan doesnt come on,could be same problem?????

[AFilip5783]

Anyone with a fix,please post..

[scottsdale]

I have a 96 grand prix doing same thing,freon full,replaced pressure switch,checked fuses and relay.anybody found cause of this,my cooling fan not coming on either

[y2kpa2]

if the switch you replaced was on the high press line that was not the high/low cutoff, that should be found on the accumulator on the 1995+ and on the compressor 1988-1995 it should only have 2 wires Good Luck!

[Laz174]

Originally Posted by 88Regal Custom

if the switch you replaced was on the high press line that was not the high/low cutoff, that should be found on the accumulator on the 1995+ and on the compressor 1988-1995 it should only have 2 wires Good Luck!

It was the High Pressure Cutoff that I replaced and it was a 3 wire plug for a 2000 grand prix. I tried everything that I could think of to test and check, but I eventually broke down and took it to the Pontiac Dealer to have it tested. They did end up finding the problem, it ended up being the 3 wire pluge that connected to the cutoff switch. The wires in the wire harness (about 8-10 inches from the plug) had actually shorted out and one of the wires was broke. I didn't even check those wires only because they were still in the factory tape job and visibly didn't look like there was anything wrong. After the replaced the 3 wires upto the plug everything kicked on just fine.

I hope this fix might help others. The dealer charged $65 for diag upto the machine and $15 to re-wire.

[na73lolz]

Hi, I have a 2004 Grand Am GT with the 3.4l engine. My AC doesn't work either (compressor doesn't kick in, and the fans don't turn on). I have jumped both sensors, checked all relays and fuses, and checked if the system was charged, but still no luck. I noticed very quickly that neither fans would turn on, even when the engine was very close to being on the red line for the temperature. I quickly checked all fuses, tested the relays, and gave the fans 12 volts and they both worked when given power. The only other thing it could be is the computer. I read on some other forums that some of the computers can partially go bad and not turn on the fans anymore. Could the computer be partially responsible for not allowing the compressor to start because the fans aren't running? I don't feel like spending the money on a new computer so I gave up on having AC and used a relay under the hood with some careful modification to let me turn on the front fans at the flip of a switch on the dash. At 231,000 miles, the money isn't worth it. I hope this can help someone maybe get closer to a solution for the fans not working!

[brcidd]

NEVER jump a three wire transducer- you can damage the PCM!

You cannot tell if system is "full" by pressure, only that therte is enough pressure to turn on compressor.

Since relay won't engage, the PCM is telling compressor to stay off- for a good reason, most likely, low pressure.- Have refrigerant extracted and weighed is always first step in a/c diagnostics.

On "W" cars as is yours- fans do NOT come on until a/c reaches 175 psi head pressure- so if you can't generate enough discharge pressure because of low refrigerant amount- then fans will stay inop...

65% of the time the system has lost refrigerant-play the odds..