Learn about Defrost Timers


Defrost Timers

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All About Defrost Timers

About Defrost Timers

A defrost timer is a cycling device typically found in refrigerators and freezers. it times the frequency and duration that the defrost heater coils melt the ice that builds up around the evaporator coils. If ice is allowed to build up, air will not be able to freely flow past them - resulting in reduced efficiency and sometimes a drastic warming of the cooling unit. Most of the time, the defrost timer is in the cooling mode, allowing the compressor to activate when the thermostat signals it to. The remaining part of the cycle (usually less than 30 minutes)the timer is in defrost mode. In this mode, it signals the defrost heaters to melt the ice build up on the coils. This defrost action is limited by the defrost thermostat.

Defrost Timer

How to buy Defrost Timers
There are numerous websites out there that sell Defrost Timers. Pay close attention to the price and shipping charges. Many websites will charge a low price for Defrost Timers, but a high price for shipping. Also, try to buy Defrost Timers from the original equipment manufacturer (OEM), if possible. This will help ensure that they are within the proper specifications for your appliance.
Defrost Timer Troubleshooting and Repair Tips
How do you know if your defrost timer is bad? One symptom would be if your refrigerator is not cooling. Although there are many causes of this symptom, A stuck defrost timer can be one of them. The timer can get stuck in cooling (compressor activated) or defrost mode (defrost heaters activated) for usually two reasons. The timer motor can fail for one.The gears can also become locked up. No matter what the reason is or which mode the defrost timer gets stuck in, the refrigerator can stop cooling. When the refrigerator is stuck in defrost mode, the compressor no longer comes on to cool the unit. If the timer gets stuck in cooling mode, the evaporator coils never get a chance to defrost, causing ice build-up to the point where there is a complete blockage of airflow past the coils. The defrost timer can also cause the refrigerator to stop cooling due to failure of the internal switch which activates either the compressor or heater coils. How do you test the defrost timer? You can advance the timer manually into defrost mode by turning the external dial until the compressor shuts off. The defrost heaters should then warm up to melt any ice build up on the evaporator coils. This mode should last 30 - 40 minutes, after which the timer should automatically advance to cooling mode. If the refrigerator does not advance to cooling mode, the timer may be bad. If the timer does advance, it is probably good. The next step would be to inspect the evaporator coils for ice build up. If they are clogged with ice, suspect the defrost heaters or defrost thermostat. Remember to unplug the refrigerator when performing any work or troubleshooting that does not require power. More on defrost timer repair and troubleshooting: The motors in defrost timers are constantly running. They eventally will wear out. They are continually trying to overcome the physical resistance of the reduction gears and the main switch. When they start to go bad, they can have a more difficult time triggering the main switch. It is at this point when they often get stuck. Resultingly, the point in the cycle where the defrost timer gets stuck is just before the switch over to the next cycle. When this happens, manually advancing the timer just a little bit will place it in the next cycle. If you experience this in conjunction with a refrigerator that seems to be stuck in one mode or the other (cooling or defrost), suspect an intermittent timer. Also consider that the defrost timer cannot effectively do its job without a properly functioning defrost thermostat, heater, and sometimes thermistor. Finally, when doing any repair on a refrigerator, check the condenser coils for dust buildup and clean accordingly.
This blog applies to Whirlpool, Kenmore, Maytag, GE, General Electric, or Friidaire defrost timers. 




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Although we offer general repair information, we recommend that a professional is hired to perform any actual repairs.

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