Question for the A/C Smart Folks.
 

This is not the 8, is the wife's car. 2005 Expedition with dual AC.

Last week, 100 degrees here, heard a loud hiss and the AC performance went down, also a bad smell in the car. Turns out the high pressure relief popped. It is located on or near the compressor. There were compressor oil all over the bottom of the compressor, but still pressure in the system.

After that, AC would only cool to 80 degrees at the vent. Pressure was 80 on the low side, 210 on the high side. Classic busted compressor.

Then it started to work, 20 on the low side, 220 on the high side. For a little bit, with 60 degree air. Those pressures mean low Freon for a 95 degree day. Then it went back to the old mode, 80/210, with 80 degree air, stayed there all day. I ordered a compressor, both expansion valves and a dryer. I still have half a quart of flush.

Today it worked like a champ, with 50 degree air on the medium fan setting (still low Freon). I figured once it got hot it would quit. Nope, shut it off to heat soak, still working. Idled for 20 minutes in the sun, still 50 degree air.

All I can figure is a piece of something got stuck for a bit in the expansion valve, the pressure blew up, the relief triggered, and along the way the debris cleared. Then it made its way to the compressor (piston type I believe, with reed valves) and hung up a valve. Then it made its way through the compressor and all is good.

That make sense?

One thought is to just drive it for a few weeks and see if it goes again. Then replace stuff. Or, return all the parts. Or, keep the parts on the shelf because I know damn well that if I have the parts, the thing will run for 100 years.

The only work I have done to this car in 11 years is a brake cylinder, fluids, 2 sets of tires and half a can of Freon a few years back.

Any thoughts?