The a/c on my car will quit blowing only when on a hour long or more trip. I'm pretty sure it's freezing up cause the fan is still running but sounding funky. Park it a while and it'll work fine. The drain is not clogged either. I suspected it being low on freon so I added a can and nothing changed. A friend checked the pressure with his gauges and it was fine albeit a little on the high side now. First thing he noticed was the compressor wasn't cycling at all, no matter what rpm the engine was at. I now assume the icing problem is due to the compressor not cycling. From what I've read here, the pressure switch is quite different from older ones but how can I troubleshoot this switch and where is it located? Any help appreciated.

 

the pressure switch should be on one of the a/c lines on the pass. side.
if the compressor is not coming on it will not freeze up.
do you feel any air coming out of the vents?

 

The compressor does not cycle on f-bodies it is a variable displacement compressor and runs all of the time. The pressure switch on the high side controls 3 things compressor off low pressure, compressor off high pressure, and fan high and low speed operation. If the fan is on medium or low and you are on a long trip it can freeze up due to low airflow across the evaporator. Two things it could be a hair low on charge, evaporator has leaves dirt etc in it, low speed fan operation. If on high speed blower and max air your pressure is 45 on the low to around 200-250 on the high side and the suction line is sweating then the charge is usually pretty close.

 

If its icing it either needs a charge or the cabin filter may be clogged up or the evaporator itself may be clogged.

 

F-bodies do not have a cabin airfilter, the evaporator catches all the crap and stops up.

 

Thanks for the help, guys.

 

explain that one how if its icing it needs charge. if it needed a charge it wouldnt be as cold.