A walk in cooler that drifts from 38 to 45 degrees will not spoil product immediately, and that is exactly why the problem gets ignored until it does. JRC repairs walk in coolers across Markham, VA for restaurants, groceries, bars and convenience stores.
We check the whole system rather than the obvious part. Airflow across the evaporator, condenser coil condition, superheat and subcooling, defrost operation, door gaskets and closers, and whether the box is simply being asked to do more than it was sized for. A cooler propped open through a lunch rush is a use problem, not an equipment problem, and we will say so.