Fridge thermostat problems: signs, testing and replacement

The thermostat is a small part with a big job. It senses the temperature inside the fridge and tells the compressor when to start and stop. When it fails, the symptoms can look like a failed compressor, which is why it is worth knowing the difference.

Two kinds of thermostat

Many older and simpler fridges, chest freezers and cold rooms use a mechanical thermostat: a dial connected to a sensing tube or capillary. Newer fridges use an electronic sensor and a control board. The fault signs are similar, but the repair is different.

Signs of a failing thermostat

• The fridge never switches on, though the light works.
• The fridge runs non-stop and gets too cold, freezing milk and lettuce.
• The fridge cycles on and off at odd intervals.
• The temperature is wrong even when the dial is changed.
• The dial turns but nothing clicks.

Before you blame the thermostat

Several other faults look like a bad thermostat. A start relay that has worn out, a blocked evaporator and a dirty condenser all cause cooling problems. A technician tests the thermostat with a meter and by bypassing it to see whether the compressor runs, before deciding.

Can I replace it myself?

A mechanical thermostat is a simple part, but it sits inside the cabinet and is wired to the compressor circuit. Mistakes cause electrical faults, and a sensing tube that is bent or put in the wrong place gives wrong readings. Switch off at the wall before touching anything, and call a technician if you are not sure.

Thermostats on cold rooms and commercial units

Commercial fridges, display units and cold rooms use thermostats or electronic temperature controllers. If a controller fails, the compressor may not run, or it may not stop. Replacing a controller is a regular call-out for us and is often a quick job.

What it costs

Call-out fees start from R250 and depend on your area. A thermostat replacement usually falls within our minor repair range of R350 to R950. Major repairs start from R1,250. We diagnose first, so you know the fault and the cost before we start.

We replace thermostats and controllers on household and commercial fridges, freezers and cold rooms across Durban. Call us with the make and what the fridge is doing.