no AC- about once a year, then OK the next day

the last 2-3 years I've had no AC for about one day in summer. And it happened again yesterday. Then the next day it's fine. I've checked the refrigerant pressure each time it's happened, the next day when it's working, and it's towards the upper end of the "ok" range. The fan runs, the AC light turns on; but the compressor doesn't engage. The next day, including today, it's magically ok, without doing anything.
I realize this is a long shot, but anyone have a similar issue and figure it out? The compressor wire connection is fully on. Maybe the contacts are oxidized? I have not tried to remove and clean/inspect it.
I have 140k miles but this isn't my DD; the AC probably has half the use on it as a typical vehicle with the same miles.

 

Does your A/C light flash when it does not work?

 

Your ac clutch most likely needs replaced.

 

Did you by chance disconnect the battery just before you noticed no A.C.?

 

Thanks for the replies.
The AC light doesn't flash when the compressor doesn't engage- it stays illuminated. The battery hasn't been disconnected recently.
Since it works 99% of the time, is there a way to diagnose the clutch other than replace it?

 

Since you don't get a flashing light its most likely not at problem with the clutch side (A/C light should flash if the A/C Amplifier doesn't see a signal from the compressor RPM Sensor when the compressor is commanded on) but a problem with the pressure sensor or thermistor (evaporator temperature sensor) or related wiring.

It's going to be difficult to troubleshoot unless you catch it when it's not working.

When it's not working you can put a jumper wire across the pressure switch to rule that out.
The thermister you will have to measure resistance and compare it to the chart and see if it's in spec.

 

I forget if it's a shared circuit, but just for funsies check and replace the fuse...long shot but easy and cheap way to rule something out.

 

Sounds like the fan clutch may be going out.

My symptoms were that the A/C would kick out intermittently mainly at long stop lights, idling and on a hot day.

 

How are you checking refrigerant pressures? Do you have a manifold gauge set?

Try checking for power right at the mag clutch when the AC is commanded on. If you have power at the clutch then it should be engaged. Try pushing it with a hammer handle and see if it clicks together

 

Without someone catching it while it is happening this will be a crap shoot to figure out. Good luck.

 

Thanks for the replies. The next time it dies I'll do some troubleshooting. I would've this time, but I was tired when I got home and it was then fine the next day when I was ready to do some checking. I don't think it's the clutch, but rather a phantom wiring/electrical issue. But I could be wrong... I drove it today and the AC worked fine and was cold. I typically only drive it once a week...

 

The easiest way to fix an intermittent issue is to instrument it, it'll never surface again while a gauge or meter is hooked up to it.