I bought a 90 model suburban a few weeks back and the ac was slightly working front and rear and lately it's been blowing around 80 degree air on a 100 degree day so yesterday I checked my low side pressure and it was at 75psi at 100 degree temps so I drained HOT AIR out of my low side valve on the accumulator until it got down to around 40 psi and I added a can of 134 and pressure is back up to around 55psi. Not blowing cold at all. Both high and low pressures are good and compressor is not cycling but running almost constantly. I found receipts in the glove box for a new ac compressor, accumulator, and switch from August of last year.

Any ideas??? I know nothing about air conditioning other than the fact I need it to haul my kids around in 110 degree NW Oklahoma heat.
Thanks, Richard Harris

Are you sure it has been converted If we are talking 134 it sounds like it was over charged to begin with. and 55 psi is high for 134 it should be around 40 psi If it has r-12 mixed with r134 that will cause all kinds of issues. Also Make sure the condensor is clean so it can reject the heat