ColdScrip Posted June 21, 2014 Report Share Posted June 21, 2014 (edited) Platform: 88 Conquest, new compressor, new expansion valve, new seals, reused lines and sensors. Problem: AC compressor keeps cycling on and off every 2-3 seconds. Belt will end of squealing eventually. Additional info: The compressor normally cycles just fine for a few moments then starts in the cycling issue. If I let it cycle for awhile I do get some cold air. My diagnosis: I studied the FSM very well. It appears that what can cause this cycling would be the AC coolant temp switch or the dual high/low pressure switch. I am thinking the switch is sensing high pressure and thus shutting the compressor off. What is interesting though is it turns back on within about 2 seconds. The dual pressure switch turns off at 2,648(384) and on at 2,059(299). I wouldn't expect the pressure to decrease from 384 to 299 within 2-3 seconds to thus have it turn back on again. The belt squealing was also interesting. Turning the system on originally before the cycling issue begins, you don't hear any squealing. The squealing appears to get worse as the compressor cycles. I have tightened the belt but it still happens. My thoughts are that the high pressure switch truly is at 384 or above but keeps turning on too soon. As a result the compressor keeps pumping every cycle. The pressure gets to the point where the compressor struggles to compress and thus fights the belt to turn it. Thus squealing. The AC coolant temp switch turns off at 235 and on again at 222.8. I have verified that it is ON and thus should not be the problem. I believe 36oz of r134a was put into the system as well as about 7 oz of oil. As a result, I believe that is a bit much r134a. Keep in mind everything was cleaned or replaced before reassembly. Going by this diagnosis do I have a possibly faulty high pressure switch that seems to turn off well before it reaches 299 or is it normal for the pressure to decrease from 384 to 299 in a couple seconds? And/or do I just need to release some freon/oil? Any other thoughts? Thanks folks. Edited June 21, 2014 by ColdScrip Link to comment Share on other sites More sharing options...
scott87star Posted June 21, 2014 Report Share Posted June 21, 2014 No mention of actually measuring the high and low pressures, have you and/or can you? Link to comment Share on other sites More sharing options...
ColdScrip Posted June 21, 2014 Author Report Share Posted June 21, 2014 That's the issue. The equipment for this is back in Ohio. Myself and the car is in Iowa. I could repurchase the equipment. I was hoping to be able to make a few assumptions without them. However I understand that only goes so far. Link to comment Share on other sites More sharing options...
ColdScrip Posted June 21, 2014 Author Report Share Posted June 21, 2014 No mention of actually measuring the high and low pressures, have you and/or can you? Actually I am just going to purchase the gauges again. The more I thought about it, the more stupid I felt as I am trying to diagnose an issue without the proper tools. I'll report back after it arrives and I have some readings. Link to comment Share on other sites More sharing options...
Crazy larry Posted June 22, 2014 Report Share Posted June 22, 2014 could also be a week relay have you tried to jumper the high pressure switch? Link to comment Share on other sites More sharing options...
JLOPEZ Posted June 22, 2014 Report Share Posted June 22, 2014 I also had this same problem, compressor turning on/off every few seconds on an 89 Conquest. It turn out to be the A/c computer behind the Ac switch control panel was bad. Link to comment Share on other sites More sharing options...
markhansenconquest Posted June 22, 2014 Report Share Posted June 22, 2014 check the ac switch on the temp water/neck...it will turn off ac if eng gets to hot and their allways broken..... rivot holding tab on is loose.... Link to comment Share on other sites More sharing options...
Recommended Posts