If your reach-in freezer is running but sitting at 25°F instead of 0°F, you’ve got a food-safety problem that needs a diagnosis today. The three most common causes are defrost system failure, low refrigerant, and a weak compressor. Here’s how to tell them apart before the tech arrives.
Defrost Failure (Most Likely)
This is the cause I see most often on reach-ins that are “not freezing” but still running. The evaporator coil inside the cabinet frosts over completely, which blocks airflow. The unit keeps running but can’t transfer cold to the cabinet.
Signs pointing here: a thick slab of ice on the back wall or around the evaporator, the compressor cycling normally, and temps that drift up slowly over hours rather than failing all at once.
The defrost system has a few parts that can fail: the defrost heater, the defrost timer or control board, and the defrost thermostat (also called a termination thermostat). Any one of them can take out the whole cycle.
A tech will manually initiate a defrost cycle and watch whether it completes. They’ll check the heater for continuity and verify the thermostat cuts out at the right temperature. Usually a single component swap once the faulty part is confirmed.
Low Refrigerant
Refrigerant doesn’t “get used up” the way fuel does. If you’re low on refrigerant, there’s a leak somewhere. Running a system that’s low on charge will eventually kill the compressor, so this needs to get fixed, not just topped off.
Signs pointing here: frost only on part of the evaporator coil (instead of the whole coil), longer run times, a freezer that slowly warms over days rather than hours, and sometimes a slight oil stain near fittings or the condenser.
A tech diagnoses this with manifold gauges, checking suction and discharge pressures against spec for whatever refrigerant your unit uses (most commercial reach-ins use R-404A or R-448A, though other blends exist). Low suction pressure is a strong indicator. From there, they find and repair the leak before adding refrigerant.
Handling refrigerants requires EPA Section 608 certification. The repair itself is typically a brazed joint or component replacement. Not a job for anyone without the right credentials and equipment.
Compressor Issues
The compressor is usually the last thing to fail, not the first. But it does happen, especially on older units or units that ran for an extended period with low refrigerant.
Signs pointing here: the compressor runs hot to the touch, draws high amperage, or won’t start at all (you might hear a click and hum). Pressures on the gauge set will be off, often showing high suction pressure and low head pressure, which suggests worn rings or leaky valves allowing discharge gas to bypass back into the suction side.
Compressor replacement is a major repair. On older equipment, it’s worth having an honest conversation about whether replacement makes more sense than the repair. That depends on the unit’s age, brand, and what else might need attention.
Other Causes Worth Checking
Dirty condenser coil. If the condenser is caked with grease and dust, the unit can’t reject heat and will run warm. Check whether it looks visibly caked. If it does, tell us when you call, and we’ll bring the right cleaning equipment.
Door gaskets or door left ajar. A torn gasket or a door that doesn’t latch fully lets warm air in constantly. Do the dollar-bill test: close the door on a bill and try to pull it out. If it slides free easily, the seal is bad. This is the one check you can do yourself before anyone shows up.
Condenser fan motor failure. The condenser fan pulls air across the coil. If it stops, head pressure climbs and the unit loses capacity fast. You’ll usually hear the difference, and the condenser area will be much hotter than normal.
What a Tech Does First
When I send a tech to a reach-in that’s not holding temp, the first ten minutes go like this: check door seals, look at the condenser and evaporator coils, listen to the compressor, and pull manifold gauges. From that, they can usually point to the right system before opening anything up. A thorough diagnosis takes 20-30 minutes. Don’t let anyone replace a compressor without doing full gauge readings and a defrost check first.
What to Check Before You Call
Two things you can do right now without any tools:
- Check the door gaskets (dollar-bill test above) and make sure the door latches and closes fully.
- Open the cabinet briefly and listen for the evaporator fan. If it’s not spinning, note that.
Anything obviously wrong, write it down. It helps us get the right parts on the truck before we arrive.
When to Call
Call a refrigeration tech the same day if your freezer is above 0°F. That’s the FDA standard for frozen food storage, and anything above it means the unit is already failing. If you’re holding dairy, meat, or prepared foods, consider whether items need to move to a backup unit or get discarded.
We cover the Bay Area and work to get you on the schedule fast, often same or next day when we can. Reach us at bayarearefrigerationservice.com, tell us what you’ve already checked, and we’ll have the right parts loaded before we show up.