AC weirdness

[watchdog]

The AC in my 2003 CVPI is doing some funky stuff. About half the time it won't work at all. The compressor won't engage and it just blows hot damp air. Then, for some unknown reason the compressor will kick in and it will start blowing cold air. Now, when it works it works great, the air is ice cold and dry and the compressor cycles like normal. The other times...nothing. Just hot damp air. I thought the system might be low so I took it to a local shop (TRWP72 knows the one) and was told that the system was charged but the compressor was bad. A 700 dollar repair. I am on this because when it works, it blows ice cold. It just doesn't work all the time. I think the shop just wanted my money. It only works intermittently and sometimes, not all the time, but sometimes if I let the car idle for a while, it will start working. I've never seen this before. I thought AC either worked or it didn't.

[86VickyLX]

Does this have automatic climate control?

[watchdog]

No it doesn't. I didn't think it was even an option on the P71. (police car)

[tjc78]

It could be the clutch on the compressor. Way back when on my 79 Continental, when my A/c didn't work I would turn it on and go under the hood and give the clutch a little tap with a hammer and it would engage.

[sly]

If you can... check that the clutch is getting signal to turn on (when it's not). Should be your typical 12-14V. If you have signal and the clutch is not engaging... see if tapping it like tjc78 mentions works. That means the clutch is worn out. If you're not getting signal... it could be the pressure sensor/switch or the temp control brain (even the manual control cars have a little electronics in there), probably loose/corroded contacts. I have heard of the issue with early 90s explorers where the AC would not turn on for about 15-20 minutes but when it finally kicked on, it was absolutely ice cold. Don't quite remember what the problem was, but I seem to think it was something to do with some sensor or the controls.

I think I'll +1 tjc78's suggestion though since that seems to fit your issue better.

[gadget73]

the later ones sometimes have problems with the relays in the climate control head unit. They also have issues with the clutch shims at times. If its got power but the compressor isn't engaging, try whacking the front of it with a screwdriver handle while the motor is running. If it grabs and goes, you need to tweak the shims. If its got no power, its probably either the pressure switch or maybe the relay inside the climate control head unit.