If you pull open the back panel of your reach-in cooler and find the evaporator coil buried in a solid block of ice, the unit has almost certainly stopped cooling properly. Ice blocks airflow across the coil and warm air builds up in the cabinet. This is one of the more common calls we get, and the fix depends on what’s actually causing the freeze-up.
Most Likely Cause: Defrost System Failure
On most commercial reach-ins, a defrost cycle runs automatically, usually two to four times a day. The heater melts frost off the coil, the melt water drains out, and the unit goes back to cooling. When that cycle stops working, frost accumulates every time the compressor runs. Over a day or two it becomes a solid block.
The defrost system has a few parts that can fail independently: the defrost timer on older mechanical units, the defrost heater itself, the defrost termination thermostat (which ends the cycle once the coil hits its setpoint), or the control board on newer electronic units. Figuring out which one failed requires continuity testing and, on modern units, reading cycle logs. That’s not a visual inspection job, it’s electrical diagnostic work with test equipment.
Second Most Likely: Door Gasket or Door Habits
A gasket that’s torn, hardened, or not seating properly lets warm humid air into the cabinet continuously. That moisture condenses on the coil and freezes. Even a working defrost system can’t keep up with that load, so you get progressive buildup.
You can do a quick check yourself: close a dollar bill in the door at several points around the frame. If it slides out easily, the seal isn’t tight. Look for mold streaks or condensation around the door frame too — those usually mean the gasket has been leaking for a while. Worn hinges that let the door sag can cause the same problem even if the gasket looks intact.
If the gasket is bad, a tech will measure and order the correct replacement for your specific door size, then verify the seal after installation. Getting the wrong gasket or a poor fit just restarts the problem.
Third: Low Refrigerant or Airflow Problems
If the refrigerant charge is low, the evaporator coil runs too cold and the surface drops below the frost point continuously. Diagnosing this requires gauges, and touching the refrigerant circuit requires EPA Section 608 certification. If you’re at this point, you need a tech.
Blocked airflow is a simpler version of the same issue. If the evaporator fan motor fails, or something is physically blocking the coil (a pan stored too close, product stacked against the back wall), cold air can’t circulate and the coil ices over. You can check whether the fan is spinning while the unit runs — if it’s not, that’s your lead.
What a Tech Checks
When we send a tech on a frozen coil call, the first step is a manual defrost to clear the ice. You can’t diagnose anything through a solid block. Once it’s clear they’ll check:
- Defrost timer or control board cycle logs
- Heater continuity
- Termination thermostat continuity
- Door gasket condition and door closure
- Evaporator fan operation
- Suction line pressure to assess refrigerant charge and rule out a metering issue
Most electrical components (timers, heaters, thermostats) can be replaced the same visit if parts are on the truck. Common makes like True, Turbo Air, and Beverage-Air are usually stocked; other brands may need a part order.
What You Can Safely Do Before Calling
Manual defrost is the one thing you can do yourself. Shut off the unit, remove the product, and let it thaw at room temperature. Put towels around the base — there’s going to be a lot of melt water. Don’t use anything sharp to chip ice off the coil. The aluminum fins bend easily, and bent fins restrict airflow and make things worse.
Once it’s thawed, check that the drain pan is draining freely. A clogged drain causes ice buildup at the bottom of the cabinet rather than the coil, and clearing it is safe to do yourself.
That’s where the safe homeowner list ends. If you find a torn gasket, a dead fan motor, or the unit refreezes within a day or two, you’ve confirmed there’s a component failure. That’s when you call.
Call Us
If your reach-in cooler is icing up in the Bay Area, we work on commercial reach-ins, walk-ins, and ice machines across the East Bay and surrounding areas. Same or next-day appointments depending on availability. Reach us at bayarearefrigerationservice.com or call directly — we’ll give you a straight answer on what it needs and what it’ll cost.