AC Compressor Short Cycles

[FJ80HI]

My 1991 FJ80 was starting to blow warm air. Got the 134a recharge kit and proceeded to fill with two cans to get pressure where gage says it should be. After filling the compressor now runs for 10 seconds and shuts off, it will come on after about 30 seconds then shut off after 10 seconds- this will continue. The ac will blow cold air when compressor is running. Did I over fill the system? I know there is a low pressure refrigerent cut out switch, some wiring diagrams indicate this is a dual low and high pressure switch. Could the high press switch be cutting out compressor? I plan to take to an AC tech that can hook some good high and low press gauges to see what is going on (the recharge kit only has the low press gauge). Just trying to get some ideas. When I look into sight glass I see flow- and what looks like very small bubbles. The high and low pressure lines to the inside of truck are warm and cold as they should be when compressor is running- problem is the short cycling.
Regards

 

[Stevesnj]

Yep it's over charged. I'd safely remove some freon before it wrecks the compressor.

 

[FJ80HI]

Thanks for reply, so I assume the 1991 models have a high pressure cut out switch?
Regards

 

[Rwhat]

1991 uses R12 unless you did a conversion to R134. I would not trust using the auto store recharge kits due to the inaccuracy of the gauges. The best way to do it is to have the system checked for leaks with either a sniffer leak detector or a UV black light and like you said have the system checked with manifold pressure gauges and start from there.

 

[FJ80HI]

The system had been retroed to R134A by PO several years ago. Last night I bled down some of the R134A and when I got to about 50 psig on the low side the compressor stayed on all the time. I bled the system down to 35 psig and all seems to work well, cold air and pressure seems ok. When I get a chance I will put some decent gages on the system.

 

[Coolstream]

Once you have gauges attached and some accurate pressure readings, you want 25-30 on the low side and 200-220 on the high side, assuming an ambient temp of 80-90 degrees.