Automotive Air Conditioning Information Forum (Archives)

chazcee on Sun July 31, 2011 6:33 PM

Year: 2007
Make: Chrysler
Model: PT Cruiser
Engine Size: 4 cyl
Refrigerant Type: R 134a
Ambient Temp: 95
Country of Origin: United States

I am far from being a PRO but I have worked on a few Auto A/Cs over the years. My poor son-in-law's 2007 PT Cruiser has a problem that really has me scratching my head.

The A/c has not worked for a couple of years but we added charge today and it is cooling. It is in the mid-90's outside but the A/C is putting out 60 degree air--but only from the far right side dash vent. As you check the air output across the 4 dash vents from right to left it gets hotter; >70, >80, 90s, over 100. That is with the heat control set to far cool and the fan on high. Also, the hot air seems to cycle off and on with the temps dropping to lower than ambient then rising again to heat output.

Has anyone out their had any experiece with a PT Cruiser HVAc acting this way? Any suggestions as to what may be wrong and how to fix it?

Thanks

GM Tech on Sun July 31, 2011 9:11 PM

Probably the evap inlet feeds the passenger side- such that when you are low on refrigerant, only that side gets cooled.....you probably have a half charge in it or less---fill it up to factory spec and see what happens....seen it many, many times-- typical low charge scenario-- driver's side is first to get warm as charge leaks out----

If indeed you did charge to factory spec-- then check it in the morning---there will be NO cooling due to complete loss of charge- due to your leak. Number one failure mode of mobile a/c systems is loss of refrigerant due to a leak.

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

chazcee on Wed August 10, 2011 8:16 AM

GM Tech

Thanks for the reply. That was indeed the problem. I got a hold of a temp/pressue chart and a guage and filled the system to spec. Sure enough it was putting out
I say WAS because after I shut it off my son-in-law went out to try it out a few hours later. When he started the car and turned on the a/c he could immediately hear the sound of a gas venting accompanied by the outlet temp going up. He shut it off and tried again later. By this time the air output at the outlets was moving well back toward ambient.

I have read a lot on the PT Cruiser forum about a faulty high pressure switch on the compressor. Do you know anything about this? I get conflicting information on its existence and the on-line auto parts places are no help as I have found the same part listed as low pressure on one site and hight pressure on another.

If it is the high pressue switch (if it exists) would replacing the compressor take care of it? We can get a reman unit for about $150 and have a guy who will put it on for another $150; but, of course, we don't want to waste the $.

Thanks

chazcee

mk378 on Wed August 10, 2011 8:40 AM

Popping the relief valve is likely because the condenser fans didn't start. On late model stuff the "switch" on the high side is typically a sensor that feeds the computer. The computer then decides to turn the fans on or shut down the compressor due to pressure. Failure of the sensor can cause neither of these functions to work, so the compressor starts, fans don't come on, pressure rises, PCM still doesn't know that since the sensor is bad, finally the relief valve opens.

Follow the high side lines around and look for a 3-wire device.