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Car Forum / Chrysler Cars / June 20072001 PT Cruiser A/C @ idle Problem
My 2001 PT has just started a strange thing a week or so ago. When I start the car and it is at idle and turn on the A/C the system seems to cycle the compressor on for a few seconds. No more than ten. Then it is off for about 30 seconds and cycles on for several seconds and then off again. The air is obviously not cool. Now, when I start to drive off the system works perfectly. Not only that, but it will cycle and cool correctly while at idle and also work perfectly if turned off for an hour or two and when started and at idle it will cycle and cool correctly. This is a problem because when I transport my mother who is partially paralyzed from a stroke, I need to set her in the car and then either place her regular wheelchair in the back or if she uses her power chair I have to pull the ramp out and load the chair in the back and restow the ramp. Living in Florida necessitates having the A/C running for her while waiting. Stepping on the accelerator and racing the engine has no effect. The Freon level is fine and the wiring is fine. There are no fault codes and I and the repair shop are at a loss. I can't leave the vehicle there overnight so they can see the problem. I am disabled myself and with the dealership so far away, I can't ride with just the windows open in 97 degree weather with sporadic rainfall and high humidity. Sorry for the long story, but I wanted to explain reasons for not letting the situation start where the repair shop or dealer can see it for themselves. The car is a limited edition with 43000 miles on it. I know we don't drive many miles. This problem seems to occur after sitting overnight. Last week it was driven three days in a row and each morning it was the same problem. Thanks Mark Of all the things I've lost I miss my mind the most. 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... > 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 [quoted text clipped - 32 lines] > > 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 >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 [quoted text clipped - 6 lines] >Glenn Beasley >Chrysler Tech 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. > >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 [quoted text clipped - 21 lines] > 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 >> >You need to see what the pressures are when the a/c is on. The first >thing [quoted text clipped - 33 lines] > >Glenn I, myself, am not checking the pressures on the A/C. I am assuming that either the Chrysler dealer or the <mechanic shop I take it to for repairs has one person who knows where to check the pressures. But I will take it back and mention this information. After all, to assume makes an a.s out of U and ME. LOL Taking the car in results in the problem not occurring. Once the vehicle is driven the compressor cycles correctly. It is just after sitting for at the very least, overnight and starting it the following day where it will not cycle correctly when initially started and not driven off. The cycling is a short on period and the air coming out is cool, just that with the short on and longer off cycle the air isn't cool enough. Once, the car is driven any distance, even a block, at even a slow speed, the compressor cycle is normal and will remain so until the vehicle sits overnight. I can leave the car idling after it is driven and the A/C will be cold and the car not overheat in this hot humid weather. And leave it idle for 15-20 minutes with only a slight reduction in the output temperature which I attribute to idling and the compressor not spinning fast enough. But it is still cold. > >> >You need to see what the pressures are when the a/c is on. The first > >thing [quoted text clipped - 39 lines] > will take it back and mention this information. After all, to assume > makes an a.s out of U and ME. LOL Not making an a.s 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. > Taking the car in results in the problem not occurring. Once the > vehicle is driven the compressor cycles correctly. It is just after [quoted text clipped - 10 lines] > temperature which I attribute to idling and the compressor not > spinning fast enough. But it is still cold. > > >> >You need to see what the pressures are when the a/c is on. The first > > >thing [quoted text clipped - 66 lines] > > temperature which I attribute to idling and the compressor not > > spinning fast enough. But it is still cold. 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 > > > >> >You need to see what the pressures are when the a/c is on. The first > > > >thing [quoted text clipped - 89 lines] > 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 |
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