I was working on a small ½ hp Tecumseh R134a cond. unit today. It was hooked up to a co2 tank and has some sort of a metering device I have never seen! I was hoping that somebody out there has seen this and explain how it works and how to properly set it up. It looks like a regular constant pressure valve but has an adjustment on the top of it like what would be on a cro or ori valve. It had like an aluminum cover screwed on top. The liquid line comes from the receiver into the side and the suction goes down into the tank to the evap. (shell within a shell). There are no sensing bulbs or sensors coming to or from it. The tank is called (Cardox) Md# 1-048-0915 Sn# T132. All I could find out was that it was made in Germany. When I put my gauges on the suction was 20” vac and head was 100psig. I figured there was a leak so I started putting in some 134a and my suction would not come up out of a vacuum and the head pressure would go up to 300psig then drop back down. I front seated the suction and the compressor pulled down to 22” vac. I disconnected power and she held there for 15 min. So I opened up everything and had bubbles in the S/G 10psig suction and 325psig head. I adjusted the valve till my suction was at 25psig and head was at 130psig. At these pressures I still had some flashing in the S/G I cleared it up and it ran like this for about 5 min. and went back into a vacuum? I am conviced that this metering device is bad but cannot find any info on it! Thought about installing a SQE and matching the cartridge to the btu rating of the compressor but not sure it this would work? Any help would be much appreciated!!