My 2002 Chevy S10 A/C unit goes on and off


Asked by Aug 24, 2012 at 05:48 PM about the 2002 Chevrolet S-10 2 Dr LS Standard Cab LB

Question type: Maintenance & Repair

The freon had leaked out from a bad vale. I replaced the valve and now when I star to recharge the system
the compressor goes on and off. The pressure reaches 55 lbs and goes down again.
Do I have to bleed the system and start over?

5 Answers


Check the AC temperture. The compressor will not stay on constantly anyway. If its still warm then maybe you need to add more refrigerant. Replacing a valve pretty much drains the entire system and can require several cans of 134 to fill completely. Also, dont use those crappy cans with the hose built in. Theyre shit. Buy an AC service hose and a can with a threaded nipple. Much better.

1 of 1 people found this helpful.

Fast on and off cycleing typicaly means system is overcharged. Ac as said before naturaly cycles but not quickly

1 of 1 people found this helpful.

An over charged system has the same symptoms as an under charged system. There are two pressure switches, one for the high side and one for the low side when one meets its set value the compressor shuts off. The low side will usually trip the system off when it drops down around 30-35psi and the high side will set it off when it builds around 150-160. An under charged system will trip the low pressure switch very quickly and over will set the high off quickly. When you replaced the valve did you evacuate the system? You put the system under a vacuum which causes all the moisture in the system to boil and suck out. Water can be boiled at room temp when put under a vacuum. If you didn't evac then a moisture build up could easily freeze causing the high side to stay pressurized which prevents the refrigerant from flowing and keeps the compressor off as well. You need a real guage set with both a high and low side on it.

3 of 3 people found this helpful.
Best Answer

55 is high. Oh, and it uses R134a, not R12 which is Dupont's trade name for freon. Did you use freon or R134a?


Freon is trademarked not R134a. You can't even get R12 without a fat stack of cash and the proper certifications. 55 psi is extremely low for the high side of a refrigeration unit.

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