Posted last night but doesn't show today.

I have to add a can of r12 every 2-3 years so wasn't surprised when ac quit cooling.

Added a can, didn't check site glass. Very little improvement. Added 2nd looked at site glass saw a little streak of bubbles that quickly disappeared. AC got cool but not cold. Drove about 30 miles and it wasn't cooling at all. Got out book and it said at 80 degrees low side should be 20-27 psi. Check and it was 0. Added some more and it quickly rose to 30. No help on cooling. Let it idle and compressor started kicking off for a minute every 4 minutes or so. In checking for leaks I found the high side was boiling the soapy water. A food thermometer read 195 F.

When I switch off the ac the low side ran up to 95 psi. Turned it back on and it dropped to about a third of the way into the red (vaccum) and stayed there. Adding more freon the compressor started laboring and stalling.

The high side connector is too small for my high side gauge connector. I suspect a blockage in the expansion valve or the dryer. Any suggestions or comments will be greatly appreciated...

Wes

Right now you are over charged. It should level off to around 80psi when shut off. You can buy the adapter to fit your high side at auto store.
Sounds to me blockage in the expansion valve. A truck of your age should have the drier replaced. Good chance of blockage. It's a filter!
Ok, here's what I'd do. At this point, if all this work is going to be done, then buy a conversion kit to R134A. If it does spring more leaks, it's a heck of a lot cheaper to recharge.

Replace the TXV and drier, vacuum the system, and refill.

Thanks to both of you, I loaded up on r12 when it was being discontinued, if I switch to 134 I can probably sell the r12 for more than enough to pay for the repair.. hmmmmm

posted last night but doesn't show today.

I have to add a can of r12 every 2-3 years so wasn't surprised when ac quit cooling.

Added a can, didn't check site glass. very little improvement. added 2nd looked at site glass saw a little streak of bubbles that quickly disappeared. AC got cool but not cold. Drove about 30 miles and it wasn't cooling at all. Got out book and it said at 80 degrees low side should be 20-27 psi. Check and it was 0. Added some more and it quickly rose to 30. No help on cooling. Let it idle and compressor started kicking off for a minute every 4 minutes or so. In checking for leaks I found the high side was boiling the soapy water. A food thermometer read 195 F.

When I switch off the ac the low side ran up to 95 psi. Turned it back on and it dropped to about a third of the way into the red (vaccum) and stayed there. Adding more freon the compressor started laboring and stalling.

The high side connector is too small for my high side gauge connector. I suspect a blockage in the expansion valve or the dryer. Any suggestions or comments will be greatly appreciated...

Wes
Replaced the expansion valve and drier. Problem was a plugged line inside the unit under the dash. The short piece of thin line was plugged with what looked to be kitty litter. Granules packed tight for about a 1/4 inch. A few taps broke it loose then I blew it out. It was only 5 inches long. Its working now.. thanks

How do you change expanson valve on 1989 hard body for a/c