True freezer not freezing

1. The condenser: clean it every 30 days

True's T-Series installation manual: "Condensers accumulate dirt and require cleaning every 30 days." The condenser is the finned coil, usually behind a grille at the bottom or top of the cabinet. When it's matted with dust, grease and lint, the unit can't get rid of heat, runs constantly, and stops reaching temperature.

• Disconnect power first.
• Vacuum or brush the dirt from the fins. True allows compressed air for heavy build-up, with eye protection.
• Brush in the direction of the fins, not across them.

True is blunt about who pays when this is skipped: "Dirty condensers result in compressor failure, product loss, and lost sales... which are not covered by warranty." And: "THE CLEANING OF THE CONDENSER IS NOT COVERED BY THE WARRANTY!" A service call that turns out to be a dirty coil is your bill.

2. Airflow inside and outside the cabinet

• Behind the unit: True asks for 1 inch between the wall and the back of a refrigerator, and 3 inches for a freezer.
• Inside: load product so it doesn't press against the back wall or come within 4 inches of it. Cold air circulates down the back wall; block it and the cabinet warms unevenly.
• The evaporator fan: if you can't hear or feel it running with the door shut and the unit cooling, that's a technician job.

3. Is it new, or just restarted?

True says to run a new unit empty for two to three days before loading it, and to let it run several hours, completely cooling the cabinet, before changing the control setting. A freezer loaded with warm product on day one, or one whose thermostat was turned down after an hour because "it's not cold yet", hasn't failed. It hasn't been given time.

On the control itself, True warns that "excessive tampering with the control could lead to service difficulties." Set it once and leave it.

4. Defrost

A freezer evaporator collects frost and needs defrosting to keep moving air. True's T-Series freezers recommend at least three 30-minute defrost cycles a day (the T-19F, T-19FZ and T-23F: at least four, of no more than 15 minutes). Defrost is ended by temperature, with a timer as backup.

If the evaporator coil inside is a solid block of ice, defrost isn't keeping up — a failed defrost heater, timer or termination control, or warm humid air getting in through a door that doesn't seal. A short temperature rise during defrost is normal.

5. The door

A torn or flattened gasket lets warm air in, which raises the temperature and frosts the coil. Close the door on a sheet of paper at several points around the frame: it should grip each time. Gaskets are a wear part — True's warranty excludes them — and they're inexpensive to replace. Check that the unit is level too: True calls proper levelling "critical to operating success", and a cabinet that leans can stop doors closing on their own.

6. Power

True requires a dedicated circuit for each unit, and says failing to provide one voids the warranty. It also says: "NEVER USE AN EXTENSION CORD," and that it won't warranty a unit that has been connected to one. Voltage drop on a shared circuit or a long cord makes a compressor run hot and struggle to start.

7. Technician territory

If the condenser is clean, there's room to breathe, the door seals, defrost is working and the power is right, True's service section points to the sealed system. It notes that light, fluffy frost only at the evaporator inlet can indicate a low refrigerant charge, and lists a malfunctioning condenser fan, a restriction, or air in the system as causes of high pressure. These need a licensed refrigeration technician — and in the US, EPA Section 608 certification to handle refrigerant.

What to tell the technician

• Model and serial number, from the data plate inside the cabinet.
• Cabinet and product temperatures, and since when.
• Whether the compressor and both fans are running.
• When the condenser was last cleaned.
• Whether the evaporator coil is iced, and whether the door seals.

Maintenance True specifies