What It Is
A defrost heater is a small electric heating element located behind the back panel of your freezer. It is part of the automatic defrost system in modern refrigerators. The name means exactly what it does. It uses heat to remove frost. Refrigerator makers introduced this feature in the 1950s so people would not have to manually chip away ice anymore.
It works together with a defrost timer and a defrost thermostat. A few times a day, the timer turns off the cooling system and turns on the heater. The heater warms up the cooling coils just enough to melt any frost that has built up. Once the frost melts, the water drips down a drain tube into a pan under the fridge, where it evaporates.
Why It Matters to You
This little heater keeps your freezer running smoothly. Without it, ice would quickly build up on the cooling coils. A thick layer of ice acts like a blanket. It stops the coils from absorbing heat from inside the freezer. When ice blocks the airflow, your refrigerator has to work much harder to stay cold.
This wastes energy and drives up your electric bill. Eventually, the ice buildup will cause the fridge section to get too warm. Your food will spoil. You can learn more about how your major fridge components work in our guide to Appliances.
Signs of Trouble
You will usually notice a broken defrost heater when your fridge stops cooling properly. Here are the most common signs that the heater has failed:
- You see a thick layer of frost or ice on the back wall of your freezer.
- The freezer feels cold enough, but the fresh food section feels warm.
- Your refrigerator runs constantly without ever shutting off.
- You hear the fan hitting ice when you open the freezer door.
- Puddles of water appear on the floor in front of the fridge.
Repair and Replacement Costs
Replacing a broken defrost heater is a common appliance repair. You can hire a professional or do it yourself if you are handy. If you hire an appliance repair technician, expect to pay 150 to 300 dollars for the job. The exact price depends on your location and the brand of your refrigerator. Always remember that costs vary widely.
The heater part itself is quite cheap. You can usually buy a replacement heater online for 20 to 60 dollars. If you decide to tackle this project on your own, check out our guide on DIY vs. Hiring a Pro to see if it makes sense for your skill level. You will need a multimeter to test the old heater for continuity before you swap it out.
How to Maintain It
You do not have to do much to maintain a defrost heater. It runs behind the scenes. However, you can help the whole defrost system work better. Keep the freezer vents clear. Do not pack food tightly against the back wall. Air needs to circulate for the cooling and defrosting cycles to work right.
Also, make sure the freezer door seals tightly. If the door gasket is torn or dirty, warm and humid room air will leak into the freezer. This extra humidity turns into heavy frost. The defrost heater will have to work overtime to melt it all. A quick wipe of the door seals with warm soapy water every few months goes a long way. This is a great task to add to your checklist during Your First Year as a Homeowner.
