If you have a refrigerant charge you should see some pressure even with your compressor not turning... after hours it will equalize on both sides of the TxValve....
It should not read zero if you have a charge... then if the compressor is running it should read more on the downstream side.... towards the condensor....

Perhaps there is no refrigerant left in the system? Maybe it all leaked out...

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That is a possibility. It may not have a charge.

I had thought the PO had told me he unhooked the compressor. Didnt' ask what that meant. The belt is still on and it spins. He told me the A/C had never worked since he owned it. He had it for 2 years I believe. He also told me he never looked into why it didn't work.

So before I add refrigerant, how do I check if the compressor is working? What else should I check?

Thanks!

Look real close at your hose connectors where they connnect to the car. Does it look like there are knobs on it? Turn them all the way clockwise and see if you get a reading then.

There is nothing like teaching a/c repair over the internet.

__________________
Jim

Okay. I see what you are saying. If I charged it, got some pressure, then by having a different pressure between the two gauges I could see that the compressor was working or not working.

Yep, they were open. That was the first thing I thought of! But seeing how I couldn't get them on in the first place, I understand the suggestion!

Actually you need to check at several different levels...
you check the compressor for ' click' by shorting out the pressure switch ( for a very short time ) at the reciever dryer... when the charge gets low it cuts out the electricity to the compressor so it is not ruined by lack of lubrication...which is brought to it by it being mixed with the refrigerant....
Also check your fuse for this system.... then see if you have electricity at the pressure switch... then at the compressor clutch when the cutout switch is shorted for the test...
then check back...

Geez Jim, I should have thought of that... those AC manifolds are not necessarily intuitive...

I just checked the fuses yesterday so they are good. Where should I connect to short out the dryer? I will put my voltemeter on it and report back.

There is a temperature switch and a pressure switch on the top of the Reciever/dryer.... just find the pressure switch...which may be the lower one.... and connect across those terminals...
Connect across both of them if you need to...just long enough to see if you hear a click...at the compressor clutch.

You should be using gloves and good eye protection when you are doing any of this stuff...
for the record....
goggles and a face shield would not be overkill....

All right.

12+ V at pressure switch

Got a very queit click when I jumped it.

No volts at clutch. Although it was hard to see if I was getting a good connection or not.

I couldn't find anywhere to connect on the temperature switch on the dryer.

And for what its worth...

While I was down there I rubbed of the soot on the compressor. It was a Four Seasons. The manufacture date was July of 2000. So I can assume it was replaced last at the same time as the conversion to R134a.

OK, start the car, do that same thing to cause the click...and have someone watching to see if the inside part of the compressor clutch assembly moves. Only run it long enough to confirm or deny the movement... this will show whether or not all things look good to the point of engaging the compressor....

Okay, will do. But I had to pack up for the night. I may be able to get to it tomorrow but may not until later this weekend.

I'm assuming if the clutch assembly moves that is good, if it doesn't move that is bad?

Thanks for all your help!
-Ryan