A/C Compressor keeps engaging then disengaging

[daizex]

A little background, I replaced my ac compressor with a used one from a buddy of mine that had the same make/model as my explorer. It’s a 96 Eddie Bauer Explorer. Since my system had no Freon in it we hooked up the new compressor, installed a new air accumulator/drier, and filled it up with Freon. The first 2-3 days after filling it up with Freon the compressor would engage then disengage, not really giving a steady output of cold air. But then on the 4th day the ac compressor stayed engaged the entire time and my air was FREEZING cold! But 2 days later the compressor went back to engaging then disengaging. I don’t have a lot of money to take it to a mechanic so I was hoping you guys might have some idea what’s wrong.

 

[my98nnj]

The compressor is supposed to cycle to maintain system pressures and evaporator temperature. Anytime a major component of the system is replaced or the system is opened to atmospher, an evacuation and recharge BY WEIGHT from a vacuum state is required to get the correct charge. You replaced the compressor, the heart.
Have a shop with an a/c machine evacuate and recharge correctly. It should cycle and blow ice cold air if it's charged correctly.

 

[daizex]

That's the one thing I forgot to mention in my post, after we replaced the compressor & drier we did vacuum down the entire system before adding the freon.

 

[my98nnj]

In that case, put a set of gauges on it and watch the system pressures. What happened to your original compressor? Did it fail internally which may have contaminated the rest of the system?

 

[daizex]

The clutch on my last compressor fried in the winter time. I remember seeing smoke from under the hood and when I popped it the ac compressor was smoky. What should the pressure be for the high/low?

 

[my98nnj]

It's really temperature dependent. Use google and get a chart. Low should be around 40 running, the compressor cycle is controlled by the low pressure switch. If the high is to high and the low isn't low enough, your orifice tube may be clogged. The gauges will tell you what's going on. Could be just a bad pressure switch.

 

[daizex]

Solved

Well after some messing around we figured out what my problem was, too much pressure in the system. The PSI in my Low pressure side was dancing around 110, which was causing the High pressure side to go crazy and get up to over 450 PSI then it would come back down to 250 PSI then shoot back up every couple seconds. Once we got the PSI on the Low pressure to around 35 the High pressure side balanced out at around 280 PSI and stayed engaged the entire time like it should and was FINALLY giving ice cold air.