I have a fitting on the vacuum pump that I can connect the yellow supply line off my gauge set to. Thus I can vacuum right thru the gauge set, then shut low side, wait for a hour to confirm it holds a vacuum. Then I can hook 30 lb 134 tank to the yellow line, purge the yellow line via the Schrader port on manifold, and at that point with a vacuum still on system open the low side valve and it sucks the gas in or the pressure from the tank pushes it in, etc. Any ideas there? Tips?

 

Sounds like you probably didn't trap any air in the system, the only thing I would have done differently would have been to charge liquid through the high side (system off) and watched for the pressure to return on the low side, this is a great way to check for restrictions. Have you tried "shopping" for A/C parts online for the 97? Just to see what metering device is available, TXV or OT? Hard to tell from the pic, but I don't see a TXV, so I'm starting to think definitely OT. They definitely can get restricted, and I'm really starting to lean that direction on this issue. I think your system is banging off on high pressure, perhaps faster than it can even register on the gauge at times.

 

+1 on restriction..500 lbs sure sounds like a restriction on the high side. Maybe you have a piece of gunk getting lodged in the OT then falling back out. The OT will be in the high side right near that fitting your pic shows. Have you ever scanned it P0530 sometimes comes on (sensor circuit failure) due to high pressure when the PCM cuts off the AC. Thought the blow out valve on the compressor goes off at somewhere near 450 lbs, apparently not in this case. By the way here is a pic that shows the mixer valve , it's the box that the high and low lines attach to on the right side of the pic. The OT replaces it.. http://shbox.com/1/vac_check_valve.jpg

 

OK, I was away for a 4 day weekend camping/ boating. On the way I called a pal that is a body shop manager at a GM dealership. I asked him to run it past a mechanic. Mechanic said condenser plugged with debris or not enough airflow while moving.. On the drive back I was thinking about this. I reminded myself to stop thinking and assuming and just do things methodically. So, I got home today and made an air scoop out of a long plastic planter and tie wrapped it on upside down to bottom of radiator support to scoop air. NO CHANGE. So, next I looked at condenser from below, looked clean but refused to assume my visual inspection is a passing grade so I pulled it out of garage and blew water through the condenser and also took the top radiator/ condenser mount cap off and blew water through there. BIGO. Working great, no high pressure cut, blowing colder air out vents when driving, etc. So, even though the condenser did not have visible debris it needed flushed I guess. I am going to a hardware store and get a sharp 90 degree elbow over next few days and come back at it more to be certain it is as clean as can be. I will post back as heat rises and a bit more time passes but it has never gone past 2 miles driving witout starting to cycle and also the vent temp never got cooler with speed and now does so I am very hopeful here.

 

Keep us updated, if that is (was) your problem I will have to remember this one..restricted condenser coil air flow causing excessively high pressure. Since the condenser blocks a lot of the radiator air surface were you having any coolant temp issues..?

 

no, not yet, but we are not quite to teh hot/ humin part of summer. But a few clues.... I bought the car last winter. They had put a new radiator in it right before. So, i bet it was the root of the problem and the new radiator masked it somewhat as far as cooling. We all learn a little. Honetly, If I were you I would take 10 mins and reach up the snorkle with a hose/ sprayer and wash out your condensor. Especially toward top 3-4 inches. Mine did not look bad at all and I never saw any debris coming out with water. I went to MEnards today and picked up a 90 degree hose adapter and am going to really get after it yet.

 

My radiator's been pulled a couple of times, AC condenser & transmission cooler once in the past few years (cam, water pump, opti installations). I always carefully inspect, clean up coils, back flush radiator and wash down stuff like that when the opportunity comes up. That's one reason I do all my own work. Good luck..