Hi all,
I purchased a new A/C compressor recently to replace one that failed. When I turn it on it usually runs for 3 or 4 minutes then the compressor kicks off and never comes back on.
Occasionally it will kick on and off as it should. If I kill the engine and restart the car, sometimes it will come back on and run 3 or 4 minutes and kick off to never kick back on again, other times it doesn't.

Anyone have any suggestions as to what to look for? Could it be the wiring causing this?

Thanks for any help.

 

What are you pressures? I thought the 93 was a variable displacement compressor, meaning it is NOT suppose to turn on and off like the 80's style compressors. Sounds to me like your high pressure is getting too high or you low pressure is too low.

Do not add Freon until you know. Adding Freon may fix a low side pressure issue but adding coolant to a system that is already over charges could hydro lock your new compressor.

 

Had my brother put the R12 in. He has the gauges and it is set optimally It will get cold when it works but just stop cooling after 3 or 4 minutes.

 

Well, Step one would be to know if the power to the compressor is shutting off or is the clutch just failing. Do you still have power and ground at the compressor when the clutch kicks off? The power should run out of the controls Through the high pressure switch and through the low pressure switch then to the compressor. If you are loosing power at the compressor it is either an electrical fault or one of those switches. Now the switches may be doing their job and turning the compressor off because of high or low pressure or the switches could be defective.

Note: when trouble shooting a car never make assumptions that something is ok just because it was just worked on. That is one of the biggest mistakes I see DYI people do, "oh it can't be that because that was just done." If the system has a slow leak you could have and issue with the low side switch turning off the compressor and if you have a cooling issue with the fan or a restriction in a line it could cause a high side issue. AC systems are very simple to someone that is trained on how they work. I doubt it would take me 10 minutes to figure out your issue if I had the car in front of me but I am only as good as the information you give me.


BTW, you did add the correct amount of oil to the compressor and vacuum the system out before it was recharged?

 

I second everything Gorn said.

I had a similar problem on my Jeep Cherokee. The AC blew cold when it was first turned on, but would shut off after a few minutes. Sometimes turning the AC off and back on would get me another few minutes of cold air, but not always.

After I verified all of the electrical connections, switches and pressures, I was left with one and only one thing - my AC compressor clutch. I measured the airgap and it was in specs but at the upper end. On a hunch, I removed a very thin shim behind the clutch and rechecked the airgap. It was now at the low end of the specs, but my AC turned on and stayed on after that. Never had another problem with it.

My point is, even if everything checks out in spec, these cars are getting up there in age and in spec at the upper end may be just enough to cause a problem like you are seeing.

 

Has nothing to do with high or low pressure as this has all been checked with gauges. Yes, the oil was added to the compressor & the system was vacuumed. When the clutch is engaged it works fine. Cold air and will sometimes run a full trip to work without stopping (75 miles one way). This is just occasionally. Most of the time it will run 4 or 5 minutes kick off and never come back on. Sometimes turning off the ignition and restarting the engine and it will come back on for about the same amount of time and kick off. Others (very rarely) it will stay on until I get to my destination and shut the car off.

 

Like I said "is the compressor getting power/ground when it shuts off", If so its a clutch issue. If not, why/where is the power stopping? Forget about the pressures right now. A switch can fail and so can the connector and the wire between. There should be a relay the power comes from then it travels through both the high pressure and low pressure switch. Its a very simple circuit.

No one can just tell you why your system is not working with out testing the electrical system. All you will get is "it happened to me and it was the relay, oh it happen to me and I had to replace the AC button in the dash, mine was stuck low pressure switch etc..."

The only why you could be sure its not a pressure issue would be if the compressor turned off while the gages where hooked up and reading.