AC issues - help
 

So I had my AC system repaired while the car was up in Chicago with Pete, and it still didn't work after getting it back, so I took it to a local shop last week. Their diagnosis was the low side pressure sensor was bad and replaced it. They also said it was about a 1/2 pound low on refrigerant, so topped off the system. Said tested it and it was blowing cold, but did say something I think is a little weird. Basically said that if ambient temp is under 80, the system is cycling compressor too often and it will set a fault and you have to disconnect the battery to clear for it to work again.

When I picked up the car, I tried the AC on the way home, and it started flashing the light on the controller, so I figured I'd give it a shot to disconnect the battery and try again. Let it sit overnight with battery disconnected, then tried it the next afternoon when temp was about 79-80 degrees out, and it almost immediately started flashing the light on the AC controller, and when I checked the code, it was 09 (low refrigerant).

Any thoughts? Has anyone ever heard/seen what the shop is saying or should I find another shop to try?

OK to reset the HVAC controls.. pulling the battery cable may reset the controls for other issues but not for 09. As posted 09 is low on Freon so you still have a leak somewhere. Time to load in the luminous leak finder dye and bring out the black light. Its still could be something as simple as a bad AC Schreader valve or? GC

So back to the shop today to double check things, and yes the refrigerant is actually low. So car will be going back in week after next (can't miss South TX ZR-1 BBQ) to try and find the leak and fix. My guess is the schraedar valve on the accumulator as when I was checking fittings after I got home, the 134 conversion fitting on it seemed a little loose. I was actually able to turn it (loosen) by hand and could hear air/gas moving. If it is the accumulator, does anyone know if I can switch over the newer (93-95) R134a version? The add-on R134a fitting on the 91 unit sticks out a good bit and looks like it would make it pretty difficult to get a connector onto it.

Sorry I didn't read your last post stating that you have R134 before I wrote the info below so it may not be any help but it explains my adventure with a similar problem.

If you have R12 refrigerant, and the repair guy installed a replacement low pressure sensor from an auto parts store, it was most likely set for R134 and their low pressure set points are different.

I had a bad LPS on my '91 that I replaced and had the same problems you describe. There is an adjustment screw in the end of the sensor and when I got it dialed in correctly, the problem went away.

You mentioned nothing about 134... You will need to change the evaporator I believe Dom found out info about the fins and a vertical vs horizontal design will not allow the 134 to flow properly unless you convert that as well. GC

should be a a/c guy here at the bbq from vintage air/he works on my cars/we have both 12 and 134/also a leak tester too

change the o rings too and refill and check for leaks the 134 stuff will leak past o rings if you don't