I have a customer that owns several convenience stores asked me to come by and look at one of his today. I don't have a lot of experience with them, so I thought I'd try here. I went the day before Thanksgiving and all indications to me were that it was low on freon. The pressures were low and the sight glass had a lot of bubbles. I added several pounds of freon, the sight glass never did clear up. He called me today and told me that the suction line and some of the compressor was freezing. I went back over there and he was right, there was some ice on the suction line and compressor. The weird thing is that it's cooling properly, everything in the cooler was between 35 and 38 degrees. Today I took the end plates off both evap coils to inspect the txv valves which is where I was leaning at first. But there was no ice on either one of the valves, everything in the box looked good. I turned the T-Stat way up to see how it was going to shut down. When the valve closed, the low side pulled down to around 6 psi before it shut off. I took the cover off the pressure switch and it was set at 25 psi, so I think that there must be a problem with the pressure switch. I don't think that's causing the problem that he's having though. What's strange is while I was looking at the pressure switch, the unit kicked back on. I turned around and looked at my gauges, the low side was at about 20 psi. So there's some pressure leaking back somewhere, I'm thinking that it may be leaking internally in the compressor. The high side won't get above 200 psi and the low side not above 50 psi. I am leaning towards a weak compressor, what do you guys think?