Defrost Thermostat Troubleshooting

Defrost Thermostat Troubleshooting

Your freezer is humming along nicely, keeping your food cold, but then one day, you go to grab some ice cream, and the entire inside of the freezer is a solid block of ice. Of course, you know that it’s time to defrost your freezer, but first, you need to figure out what went wrong. One possible culprit is your defrost thermostat.

You know your defrost thermostat is broken if the fridge freezes over or doesn’t defrost. If the freezer begins freezing solid, this indicates that your defrost system has failed, which will eventually cause your fridge to stop cooling completely.

Defrost Thermostat

Fortunately, defrost thermostat troubleshooting is something we do here at RA Appliance Repair. While you can do simple inspections yourself, it requires professional skills and tools to properly fix your broken defrost thermostat in a short amount of time.


What Is A Defrost Thermostat?

A defrost thermostat is a safety device that allows your refrigerator or freezer operation while guarding against excessive energy usage and food spoilage caused by extended freeze cycles. The thermostat will cycle on for a programmed period during regular operation and then shut off. Then, after a programmed time interval, it will turn back on again to restart the cycle. Defrost thermostats are typically located near the freezer section of your refrigerator or freezer.

For most refrigerators, the defrost thermostat is a simple wire with a mercury bulb. When it gets warm inside the refrigerator, the liquid starts to expand, making the wire complete an electrical circuit to let power flow through it. This turns on the heater that defrosts or melts any ice in its way. When the mercury cools and starts to contract, it opens the circuit and stops the heater.

There are many different reasons why the defrost thermostat in your fridge may not be working correctly.

  • Incorrect defrost timer

A malfunctioning defrost timer can lead to the development of ice on the evaporator coils, which will cause poor airflow through them and overheating in the refrigerator section.

Incorrect defrost timers will have a timer plunger that only moves partway or doesn’t move at all during the defrost cycle. This will cause ice build-up because there will be no opening of the freezer door during defrost to let the warm air into the refrigerator’s freezer section.

  • Broken or defective thermostat

If you’ve used your defrost timer before and had it replaced, this may be the problem since most technicians will only replace the defrost timer with an identical part number. The correct replacement for a broken or defective defrost thermostat is either a service kit or the entire defrost control assembly.

  • Defrost heater problems

The most common problem with the defrost heater is that it’s burned out and needs to be replaced. This can happen if things like aluminum foil or plastic bags are left where they shouldn’t be, which could melt onto the heating element and damage it.

  • Other causes for defrost problems

Other common problems are when the evaporator fan isn’t working, which will cause low airflow over the coils, and when there is damage to the freezer section of the refrigerator. This includes rust or dents on the evaporator’s cooling fins or coil tubes (usually caused by a child trying to climb inside the fridge).

If you’re unsure of what’s causing the problem, it might be best to get help from a professional technician before trying anything yourself.


Signs Of A Broken Defrost Thermostat

A refrigerator defrost thermostat is a device that regulates the amount of time an electric current can flow to the refrigerator’s heater. When you turn your refrigerator on, the compressor starts and forces cold refrigerant into the evaporator coils. Ice then forms on these coils, blocking air movement through them. The defrost system dissipates this ice buildup to allow airflow.

refrigerator's heaterA broken or faulty defrost thermostat allows the heater and fan to stay on continuously, resulting in a warm refrigerator and spoiled food. An open-circuit thermostat prevents the compressor from running, but it will not prevent the evaporator fan from running all of the time if connected directly to one of its terminals.

The fan will continue to run and the evaporator coils will defrost themselves, resulting in spoiled food and warm conditions inside your refrigerator or freezer. A faulty defrost thermostat also allows the evaporator fan to stay on even during normal operation, resulting in elevated energy usage and high utility costs.

Here are six signs that a defrost thermostat may be broken:

  • Ice buildup on the evaporator coils is more severe than usual.
  • The refrigerator or freezer temperature is warmer than normal.
  • There are indications of a broken fan blade, such as loud rattling when it runs, bent blades or chipped plastic from the blade hitting the housing.
  • The evaporator fan runs non-stop when the refrigerator is turned on.
  • There are frequent fluctuations in temperature inside the refrigerator or freezer.
  • The condenser, compressor and evaporator coils are visibly dirty, which suggests that the defrost system failed to remove melted ice from them for an extended period of time.

A broken defrost thermostat can cause severe problems with the refrigeration system. If you suspect that there is a problem with your refrigerator’s defrost thermostat, have it repaired by a professional technician immediately.


How RA Appliance Repair Works

When it comes to appliance repair Toronto, no other company beats the professional hands of RA Appliance Repair. We’ve been dealing with all appliance problems for years and continue to provide exceptional services at the most affordable costs.

We understand your frustration when you’re dealing with defrost thermostat problems in your refrigerators. That’s why we make it a point to be available whenever you need help.

Ø  Same-day Appliance Repair

Ø  Competitive Appliance Repair prices

Ø  Excellent Customer Service

Ø  High-Grace Appliance Replacement Parts

Ø  Specialized Appliance Repair

Ø  Appliance Retail and Delivery Service

No job is too big or too small; we do them all! Our team arrives fully prepared with the needed equipment and skills to get the job done in no time. Schedule your appointment today!