I've had a problem with a walk-in cooler that is intermittantly dropping below freezing (usually around 18 degrees). The customer originally called with frozen product and by the time I got there it was cycling normally. Pressures were good. I checked the bulb on the TXV and there was no corrosion and it was in the correct position. I concluded that it had to be a thermostat sticking and changed the thermostat. A week passed with no problems and then the customer called back with the same complaint. I checked the system again with no visable problems. I marked the thermostat just to make sure no one was adjusting it (it is behind the coil and out of sight) 3 weeks went by and the same problem occured. I did adjust the position of the thermostat bulb on the evap coil, hoping that this will make a difference. I have never been able to catch it not cycling on and off. The customer is getting frustrated and so am I.
Anyone have any suggestions?