I have a 1996, Chevy Cheyanne, 270,000 miles, and it is an automatic transmission.
So, this truck has been a project truck from the beginning, and the AC was no different. It had some missing components, and so we put in all new ones except for the evaporator. Then, my brother charged it with a propane/butane mix and it worked pretty well after that. recently I decided to do it right, so I vacuumed the system and tried charging it with R134a. When I put in only one 12 oz. bottle, the compressor stayed engaged and ran the high-side pressure to 300+ psi, and the low-side pressure was around 20. When I turned off the AC the high and low pressure equalized at 90 psi. I did some research and then cleaned the evaporator and put in a new orifice tube. I still got the same results. Your advice would be appreciated.
Something is blocking your evaporator, or in the vicinity of the evaporator. 300+ PSI is way too much pressure. Did you replace your receiver/dryer? You were insane to be driving around with propane and butane in your system, those things are obviously EXTREMELY flammable and they weren't designed to be compatible with PAG oil.
Thank you for being patient with me, we have been very busy the last while and with winter here I don't feel the need to have cold air. So we replaced the dryer when we replaced all those parts it is almost brand new. Would you start by replacing the evaporator, or are there other diagnoses to do first?
How quickly did the pressures equalize?
It was like 2 or 3 seconds