Hi, first time posting here, so you'll have to bear with me. I have a Norlake freezer model # ZF122SMS/0-2 Serial # 99120491 that I cannot get below 0 degrees at best mostly hangs around 3-6 degrees. Now just for some brief history....When I first started on this thing it would hold -5 easily, the box temp. began to creep up slowly, I cleaned the condenser thoroughly and right back down to -5 or better. I also repaired a short causing the fans to stay on all during defrost. Never touched the refrigerant circuit. Well, about a month later the temp. was back up again, there was no low side port so I frontseated the suction service valve and put a swivel tee on to accomodate the LPS. This is 404-A with Sporlan EFS 1/4 ZP 1/4" * 1/2" ODF. Copeland condensing unit 1/2 HP compressor, no receiver, HeatCraft evap. Model # CCL16AF Serial # D99HOO362. I found that the evap. was being starved to death, frost pattern on the coil was only the first row if that, and running around 50 degrees superheat. I had no reason to believe there was a leak but I recovered the 23 oz charge anyway and took the valve apart. I found some, what I would call "residue", black in color around the port and on the needle and carrier. I cleaned the internal parts of the valve and reassembled, installed a new drier. Leak check with Nitrogen, Evacuate, charge. Once the temp. was at about 6 degrees, it would go no lower because I couldn't get the saturated suction temp. needed to get below that, adjusting the valve would only cause flooding (0 degrees superheat at compressor) or would starve the evap. again, absolutely no modulation from TEV at either condition. Head running around 305 and Back will not drop below about 25 psi. It will if I turn the setting on the TEV in all the way in which case I completely starve the evap. So really my problem is that I cannot achieve the suction pressure I need to be at with a full evap. I've spoken to a Sporlan rep. and He suggested that the compressor may be at fault, not able to achieve the compression ratio I need, I valved off the suction line and the compressor will pull about a 10" vacuum and hold it. I need help! Things just aren't adding up, pressurewise on my gauges it looks like I have a full evap. and when I open the TEV by adjustment the head skyrockets and so does the back naturally but superhaet is either flooding or starved. Subcool is around 2 degrees at best. I've been through so much crap with this thing I'm sure I'm leaving out important stuff but if anyone has any Ideas at all I'm all ears. Thanks in advance!