True Lowboy Freezing- We have a True TSSU-48 that is freezing up completely. We have the temperature contralto the lowest setting. Is it just the Temp Control kit that would need replacing or is it something else? The coils are cleaned and dust free.
First defrost it and set the temp control to the middle of the range. Assuming you have a mechanical temp control. Watch for build up and raise it if it does. Make sure to check the door gaskets and for any source of water retention like a faulty drain line or leaking evaporator pan. They will increase icing drastically. Also uncovered warm product.
Often the controls get replaced with the wrong one or not bonded to the evaporator coil. With The common replacements that are usually made by Ranco, the A-32 series moves both the cut in and cut out temperature. But the proper A-12 ones have a fixed cut in of between 36 and 39 degrees (depending on model) to facilitate defrost every cycle.
if a cap tube system the thermostat sensor is usually located near the middle of the evaporator. if low on charge, or the cap tube is partially restricted, the thermostat will not sense the proper temperature and the coil will ice up.