Nissan D21 4cyc ac compressors keep failing

[jamman32]

I have gone thru four compressors now. I have flushed the system, swaped the compressor, dryer, and expansion valve four times now. The system works for about a week, and then the compressor starts to squeal. Eventually the compressor seizes and throws the ac belt. I am at a loss to the problem. I was wondering if this could be a bad high pressure switch. I was thinking that maybe the pressure builds, and that the compressor is never told to shut off, thereby overloading the compressor. Any and all ideas are welcome. The last two compressors were new and installed by a professional shop. They seem to be at a loss as well???

[boriquaS13]

Do you happen to know what your a/c pressures are? Low and high?

If your high side pressure is to high you may have a problem with your fan clutch or condenser fan (can't remember if your truck has one or not). High pressure in your high side can destroy a/c compressors quickly.

[jamman32]

No fan clutch... Thats why I was thinking the high pressure switch could be bad. What controls the cycling of the ac compressor on and off to keep the pressure with acceptable norms???

[boriquaS13]

Your truck should have two switches low pressure cycling wich is for your a/c compressor to cut on and off but it usually only cuts the compressor of when the pressure gets to low to prevent the evaporator from freezing. Now the high side switch should cut the compressor off at a certain pressure usually really high. Do you have any a/c gauges that you could hook up and actually see the pressures it would help to diagnose your problem because most a/c diagnostics is done by the pressure readings.