Last weekend I replaced the A/C compressor, condenser, accumulator/dryer and liquid line on my 98 XJ. (Thanks djb for the advice and answers on this job.) I put 7oz of PAG oil in it. The system holds 8.1oz, but I didn't flush the evaporator, so there was probably still some oil in the there, FSM says it can hold up to 2oz itself. I had a shop pull a vacuum on it for an hour then charge it up. Ah, finally nice cool air...

Fast forward to today, I get off work in 85* temps and start to go home. A/C works good for a few minutes and then I turn the fan up and it dies. I get really mad and turn the switch off and on until it I can tell the compressor engages again. The A/C blows cold as ice while I drive around for an hour waiting for it do it again. It doesn't, it works the whole time.

When I get tired and go home and park, in my driveway I fiddle with the switch and find out that if I slowly turn the blower from 2 to 3, that disengages the compressor?!? If I switch very quickly from 1 to 4 it stays engaged, it only turns off the compressor when I casually switch from speed 2 to 3. I wouldn't believe this if I wasn't able to duplicate it at will. My a/c works great as long as you don't change the blower speed from 2 to 3.

My first thought is a faulty HVAC switch, but they run about 200$ new, so I wanted to ask the great minds of CF if they have any idea why changing the blower motor speed would disengage my a/c compressor? Any other things to check?

 

You can an entire used HVAC climate control panel off eBay. Check them out.