I have a cold food vending machine that is giving me fits. At first the evap was freezing up. I leak tested, replaced dryer, evacuated the system and recharged with 12 oz of R134 as per the mfg. The label says 12 0z R134 and the design pressures are 90 lbs low side and 230 high side. I checked all fans are working fine, I start the unit and the pressure on the high side slowly build to about 240 and then the compressor shuts down. It looked like a possible overcharge situation so I removed some of the charge. Unit runs longer, but when I put the enclosure back together compressor goes down again. I then remove more charge, still goes down. If I cut the charge way back the unit will run longer but it will not get cold enough, I checked the expansion valve and it appears to be working correctly. Any ideas on what I should do next?
Thanks.