This may or may not be the place to ask this question but here it goes. My 97 f250 psd has AC but when you turn it on the AC compressor clutch doesn't engage. Old lady I bought it from said it wouldn't hold a charge. I put a gauge on it today and it's showing a good charge. So where should I start on trouble shooting this AC problem.

 

The pressure switch on the pump has been known to go bad, jumper it and see what happens. I believe there is also a pressure switch on the expansion tank on the passenger side.

The wires at the front of the AC pump could have a bad connection too.

 

Low pressure switch on the dryer is probably bad. The one on the compressors is the high pressure switch.

Turn the a/c on and jump the two wired on the dryer. If the a/c turns on then the switch is bad

 

Where's the dryer at and how do you jump it?

 

Black round canister on the passenger side by the ac blower. You'll see a two wire plug on it. Unplug it and use a wire to connect the two wires together.

 

If doing what Mike is telling you to do doesn't engauge the AC compressor, Try wiggling the high pressure switch connector. It is a 2 wire connector located on 1 of the Freon lines just behind the AC compressor. I have had to "adjust" the pin in that connector.

 

Ok so I tried jumping the low pressure switch with a paper clip. Nothing happened. This was with the engine running and ac turned on. Also with the engine running I took a volt meter to the low pressure switch and got 14 volts there. Tried the high pressure switch and couldn't get anything, then I tried the clutch solinoid plug in and didn't get any power there either. Is this normal?

 

Have you checked the fuses

 

I did. I only found 1 fuse under the dashboard that was labeled for the ac.

 

When you tested for voltage at the high pressure switch, was that with the paper clip jumper in the low pressure wiring plug? If the jumper was in place, you should have voltage on 1 of the wires at the high pres. plug. I believe the juice runs from the in cab AC switch to the low pressure switch, to the high pres. switch, to the compressor clutch.

 

Went back out and while the low pressure switch is jumped I have 14 volts at both the high pressure switch and the compressor clutch switch. When I plug the low pressure switch back in, I can't get any power at either the high pressure or the compressor switch plug. But all the time the compressor clutch does nothing.

 

Either the system is low on Freon, or the low switch is bad. With the key on and engine off, paper clip in low pressure wire, AC clutch unplugged, plug the clutch in. You should hear the clutch click. If no click the magnet in the clutch I shot, and the clutch needs to be replaced. Take a 1/2" wrench and try to turn the bolt on the front of the compressor. The whole inner part of the clutch should turn fairly easy. If you can't turn the compressor, it has locked up, and a full AC service is needed, compressor & dryer replaced, system vacuumed out and recharged.

 

Good info. I need to do some of this too.

 

I'm gonna say you have a bad clutch.

 

So I tired it again. Key on ac turned on, low pressure switch jumped I hear no click on the ac clutch magnet. What all is involved in changing out the ac clutch? Do you have to pull the compressor?