Ice on the evaporator coil is a symptom, not the problem. Here are the four causes we see most and the two you can rule out yourself.
A walk-in that is icing up is telling you that warm, wet air is getting in faster than the coil can handle, or that the coil is not defrosting when it should. Both are fixable. Neither is fixed by chipping the ice off.
The two things you can check
First, the door. Stand inside with the lights off and look for daylight around the gasket. A torn or flattened gasket lets in a surprising amount of humid kitchen air. Second, the door closer. If the door does not swing shut on its own, staff will leave it cracked during a rush and the coil pays for it.
The things we check
Defrost timer or control board, defrost heaters, the evaporator fan motor, and the drain line. A clogged drain line is a very common one: melt water backs up and refreezes on the coil every cycle.
If the coil is a solid block, turn the unit off, prop the door, and move product to another box while you call. Running it frozen just stresses the compressor.
