Porsche Repair: 1988 Porsche 944 A/C, porsche 944, luck dave

Question
Dave,
I have just added a third can of R134a to my car and the compressor kicks on for a split second then off.  Just won't kick in for any duration.  This continues as the car is running.  The pressure seems fine, did I overfill or do I have a sensor problem in the car.  Relay is fine, fans work fine.  Can you help?

Thanks in advance
Timothy Smith

Answer
Timothy,

Air conditioning is not an area I've dealt with much...turning on the air in my 356 is just a matter of rolling down the window...and then the other.

I found a reference manual that describes your problem as:

Temperature control switch malfunction, rapid cycling, all other functions appear normal.

It discusses the likelihood that the "feeler bulb" (sensor) is either mislocated in the evaporator coil or it is malfunctioning.  If its determined the feeler bulb is properly located (I can only assume that it wouldn't be properly located if it seems disconnected from its mounting or seems out of place), then the switch should be replaced.

Now before you go replace the switch, I'd consider another opinion or two.  The following links, (which I found fairly quickly this morning) suggest system pressure is another cause for rapid cycling:

http://www.volvospeed.com/Repair/ac.htm
http://experts.about.com/q/1591/480153.htm

Sorry I can't be more definitive.  Good luck.

Dave