I went into a local marine refrigeration shop and talked with a technician. It wasn't a very satisfying talk, but it left me with a few things to check as well as a bit more knowledge.
Most devices from different manufacturers seems to use the same compressor and control unit. The set of plugs is exactly the same, with the bottom two pins being where the thermostat control plugs in. He suggested shorting those two pins for a day or so to run it continuously and see how cold the system would get. If the second cold plate, in the fridge, ices over, that indicates that I've got the right amount of refrigerant, and my problem is simply related to the thermostat.
My problem seems related to the thermostat, and I may try getting a new one and installing it.
Symptom:
- Compressor will not turn off
Possible cause:
- Faulty Thermostat
- Incorrect Thermostat probe installation
- The thermostat may have continuity (on) but might not turn off. The system may run continually. Frost or active cooling may develop from the return line tube on the plate (second plate) to the compressor.
Check & Test:
- Check that the compressor will turn off with the thermostat knob in the off position.
- Remote Thermostats work best when any excess capillary tube is in the cold space.
- If the thermostat is a Remote or ETT the bulb must be clipped on the side or bottom of the cold plate. The best location would be the coldest section of the plate.
Remedies:
- If the compressor does not turn off with the thermostat knob in the off position, replace the thermostat.
- Check that the thermostat bulb is in good thermal contact with the cold plate. The bulb probe must be on the second plate in a two plate system. This is the plate without the valve.