2001 PT Cruiser A/C @ idle Problem

You need to see what the pressures are when the a/c is on. The first thing to check is the A/C fan assembly. When the A/C turns on the outside radiator fan has to turn on, if it doesnt the system will go into a high pressure on the high side and cut the compressor off. This will cause your lack of cooling at idle. Driving down the road the A/C should work ok due to forced air across the condensor by driving. You may also be experiencing a higher then normal engine temp at idle.

Glenn Beasley Chrysler Tech

Glenn - I have a question... First, thanks for your response. I am running into a similar problem with my PT Cruiser. If you turn on the air conditioner - what triggers the radiator fan to turn on? Should the radiator fan be running whenever the AC switch is engaged?

Here is the path I've been down. Might be conspiracy theory - but - maybe you can tell me if I'm nuts...

We initially fixed a pressure problem on the low side by replacing the receiver-drier assembly. Recharged the system to find out the high side pressure was off the scale. Radiator fan wasn't turning when the AC switch was turned on. The non-dealership tech tracked down a wiring diagram for the fan/PCM assembly, checked both relays, and found that the PCM wasn't supplying a ground to the fan when AC is switched on. He could artificially ground the fan -- and the AC would work. This led to non-dealership tech telling me that PCM needed to be replaced.... Initial thought was that he was nuts and I went to a dealership to get it checked.

Dealership came back and definitively told me it was the radiator fan

-- even though the fan was operational on engine temperature control relay. Replaced the fan -- AC worked for a about 2 days, cool weather. I'm now back in the same situation. Went out to check the car before returning to the dealership to find the fan not spinning. If I turn on the AC, the fan does not engage. Service Rep is telling me this is due to the lack of freon in the system -- which they believe is due to a bad high pressure vent on the compressor. The PCM is still able to engage the fan for engine cooling, and I'm not seeing any temperature/overheat issues.

Question is... Am I a victim of Chicken / Egg theory? or is the fan not getting a signal to turn on from the PCM and causing the freon to vent.....

Thanks...

The fan dual speed electric fan. It will always turn on when the a/c is on unless the system is out of R134. The pressures will go extremely high if the fan does not turn on and possibly blow the R134 out of the system causing a low charge. The first thing to do is check for proper charge. This may require a recover/weight and recharge procedure Your PT has 2 a/c ports at the top near the passenger side and one at the bottom near the a/c compressor. DO NOT USE THE HIGH SIDE PORT AT THE TOP< USE THE HIGH SIDE PORT AT THE COMPRESSOR. If you use the high side port at the top it will not give you an actual reading and will cause a problem due to false high side readings. (High side pressure will show low at all times on this port). The radiator fan operation is control by the Powertrain Control Module with inputs from the temperature of the coolant, which is sensed by the coolant temperature sensor, and vehicle speed which is measured by the vehicle speed sensor. The PCM turns on the fan through either the high or low speed fan relay. The PCM provides a ground to the relay's control circuit. The PCM grounds the fan motor to engage it. If the motor is open circuit it will not turn on.

Glenn

Pressures are normal. Fan runs when A/C is turned on. Fan runs in low and high speeds as needed. Forgot to state those facts. As when I stated before (including this new information) all things except the cycling run fine. Car never overheats. That surprises me since there is no room in the engine bay for a cockroach to pass through sideways with it's stomach sucked in! LOL. The only work done on this car besides the normal maintenance, recalls and regular manual listed mileage service is there was a leak in the tranny vacuum modulator assembly at the tranny. Had that replaced, new trans filter/fluid/flush/gasket et al. Found thermostat was stuck open and replaced it. A small leak in the radiator and had that replaced. Thank God for aftermarket extended warrenties !!! My regular TRUSTED repair center and the dealership have no clue. They cannot repeat the problem and find no fault codes. They state the pressures are fine.

OK one more time, Are you having the A/C pressure checked at both ports near the passenger side strut tower? If so you are NOT reading the high side pressure. It has to be checked down at the A/C compressor discharge port or the reading will be false. If you are experiencing a high pressure the compressor will cut on and off and not cool at all. IF the system is working when the tests are being performed it would be hard to say what the problem is. Have you taken the vehicle in when the problem is happening?

Glenn

I, myself, am not checking the pressures on the A/C. I am assuming that either the Chrysler dealer or the

Not making an ass out of me!! LOL Once again, it is a dual speed motor and when the A/C is turned on the radiator fan must turn on also or it will develope problems. It does not turn on from a high pressure switch. It turns on when the request for the compressor is seen.

Glenn

If I may add to the previous AC questions asked above; I also have a

2001 PT Cruiser that had air conditioning last year, but didn't work starting this summer. I have taken it to my mechanic and had the compressor replaced (because everything else checked out ok) and still the compressor will not engage. I am told that the R134 is at the proper pressure and that the compressor can be jumped. Even when the compressor is jumped, there is not any cold air, because the fan does not come on.

The fan does come on when the radiator temperature tells it to cool, but from what I have read above, this should come on when I turn on the air conditioner.

My mechanic says that there is an electrical problem, but has not gotten around to tracing it. The temperature is starting to get real hot, and I would love to have my air back. Is there anything I can tell my mechanic to try before cutting open the wire harness?

Thanks in advance, Jack

It sounds to me like the technician isn't familiar with the vehicle. The Fan MUST come on when the A/C is requested. If the technician that is working on the vehicle is using the A/C ports at the passenger side shock tower he is not getting the proper reading. The high side MUST be checked at the high side fitting down by the A/C compressor to get the correct reading. I would be willing to bet that the compressor is kicking out because the high side cut out switch is turning the compressor off and the reason it is going high is because the fan assembly is bad.\

Glenn