Symptoms of a Bad Refrigerator Thermostat

When it comes to appliances, the fridge gets taken for granted until things start to go wonky. There's a lot going on in a fridge — components aplenty can all affect performance, like the coolant, condenser coils, door seals, the thermostat and even the ambient temperature in the living space. Common issues include erratic behavior from the thermostat or even complete malfunction. But how do you know it's the thermostat and not one of the many other potential troublemakers?

One jug of milk turning sour before its "best by" date is bad luck, but a pattern of sour-too-soon milk indicates something's going wrong. When all things perishable go bad before they're expected to, it's time to investigate. Or maybe it's going the other way around. Perhaps your lettuce has frozen patches, and things that should be simply cold are thickening up into semi-frozen slushes.

Sometimes, inaccurate thermostats can lead to things like the motor firing up more often than it should, so you'll hear the fridge more often, too.

In regard to food safety, a consistent temperature inside the fridge is critical. If the freezer is freezing food — even if it freezes it too cold (yes, that can happen) — then that's fine because frozen is frozen, but the fridge being inconsistent and having warm pockets can lead to invisible foodborne illnesses along with things visibly spoiling too soon. It's those invisible deteriorations that are cause for alarm.

The safe range for a fridge is 32 to 41 degrees Fahrenheit, according to Mr. Appliance. The problem is, the thermostat may display those temperatures, but still be inaccurate. So how can you test the accuracy of the thermostat?

Time to use a little science and see if the thermostat is the problem or if your issues lie elsewhere. You'll need an accurate instant read thermometer, like a kitchen cooking thermometer, to do this. First, put a glass of water in the fridge and a glass of cooking oil in your freezer (the oil won't freeze, and you can still cook with it later). Close the doors and leave them for a few hours or overnight.

When the time passes and each is sufficiently cooled to reflect the ambient temperature in the fridge and freezer, then record the temperature in each glass and write them down so you don't forget. Now adjust the thermostat according to your fridge's manual specifications. A couple degrees colder or warmer, whatever you need for reaching optimal temperature. Now, it's waiting time again — give it 12 hours to reach the new temperature.

When it's time, take the temperature for the water and the oil again. Did the temperature move up or down, according to your thermostat adjustment? If so, then great, maybe you just needed to change the temperature. Maybe the thermostat dial was bumped by a milk jug or somebody's tiny fingers wanted to tinker with the tech. If the refrigerator temperature control is not working, then you may need to replace your thermostat or have a service technician pay a visit.

If adjusting the thermostat got you the colder/less cold environment you sought, then you may have other issues affecting your fridge's performance. Be sure you check that your condenser coils at the back aren't coated in dust, that air grates aren't blocked inside and that your door's seals are nice and clean. Remember, even just being unlevel can affect a fridge's performance.

But if you at least know the thermostat works, then you've crossed one possibility off the list.