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Posted on Jun 01, 2008
Answered by a Fixya Expert

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Defrost heater not cycling

I have a KitchenAid refrigerator that wont run the defrost cycle and the evaporator keeps frosting up. I have replaced the bimetal twice and the defrost control board has been replaced once. The trouble still persists. I have checked the bimetal and the resistance is about 2 to 3 ohms when chilled. I can place the refrigerator in the test mode to check the defrost circuit by unplugging it, turning off the thermostat and plugging it back in after a 30 second wait. The defrost cycle will work if I jumper across the test terminals that bypass the bimetal. If I try the same procedure without jumping out the test terminals, the relay in the defrost control board operates and then drops back out about 30 seconds later.

  • MikeDaniel Jun 15, 2008

    Your diagnosis was real close. This ADC is an adaptive type defrost controller. The brown lead that ties between the defrost thermostat and the defrost heater back to the ADC is a feedback lead that lets the controller know that the defrost thermostat has opened. When this happens the ADC removes power to the defrost circuit. This brown lead was going open intermittently somewhere in the harness between the connector in the refrigerator and the connector in the freezer. This open was making the ADC think that the defrost thermostat was open and removed power to the defrost ckt.



    This had been head scratching trouble for me. I started by first replacing the defrost thermostat. That didn't help. Then after talking to several technicians, I was told to replace the ADC. That didn't help either. I then started reading everything I could find about adaptive defrost controllers. That's when I discovered about the feedback control leads and started thinking about the possibility of a trouble there. Your post got this part started. Thanks again. I had to run a lead throught the return vent between the freezer and refrigerator to bypass the harness. This fixed the problem after about 8 months of manually defrosting this refrigerator weekly. Thanks again for your help.



    Mike Daniel

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1 Answer

MARLON KELLER

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  • Expert 111 Answers
  • Posted on Jun 01, 2008
MARLON KELLER
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Sound like to me you have a wire terminal short on the neutral side between you def. t-stat and the adc
go to www.servicematters.com for the service bulletin on this issue


If you need further help, reach me via phone at https://www.6ya.com/expert/marlon_56d9a24f02585258

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Delafield 6000xl trips main breaker after about 10 or 15 minutes little screen at top right says def which I'm guessing that's defrost

The Delafield 6000xl tripping the main breaker and displaying "DEF" on the screen could indicate a problem with the refrigeration system's defrost cycle. The defrost cycle is necessary to melt any built-up ice or frost on the evaporator coils and maintain efficient cooling. If the defrost cycle is not functioning properly, it could cause the unit to overheat and trip the main breaker. To troubleshoot this issue, you can try the following steps: Check the defrost timer: The defrost timer controls the duration and frequency of the defrost cycle. If the timer is not functioning properly, it could cause the defrost cycle to run too long and cause the unit to overheat. Check the defrost thermostat: The defrost thermostat monitors the temperature of the evaporator coils during the defrost cycle. If the thermostat is not functioning properly, it could cause the defrost cycle to run too long and cause the unit to overheat. Check the defrost heater: The defrost heater melts the ice and frost on the evaporator coils during the defrost cycle. If the heater is not functioning properly, it could cause the defrost cycle to run too long and cause the unit to overheat. If you are unable to diagnose and resolve the issue, it is recommended to seek the assistance of a professional refrigeration technician. They will be able to diagnose and repair the problem to restore proper operation of the Delafield 6000xl refrigeration system.
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Fixya manuals

It doesn't defrost
  1. Defrost control board
If the defrost function is not working on your refrigerator it could be an issue with the defrost control board. This control board oversees several internal conditions and regulates the activation of the defrost cycle. A faulty board can be the primary reason your refrigeration unit is not transitioning to the defrost cycle. Over time, the buildup of ice on the evaporator coil will prevent the refrigerator and freezer from maintaining proper internal temperature. It is advisable to first check the defrost heater and the defrost thermostat for continuity prior to replacing the defrost control board.
  1. Main control board
A possible cause for a refrigerator not defrosting, especially on more modern units, is the main control board. The main control board acts as a "brain" for the unit controlling the defrost cycle, compressor, and run time, and essentially acts in place of the defrost timer. The control board can be tested using an ohm meter for functionality and will need to be replaced if bad.
  1. Defrost timer
If the refrigerator is not defrosting the timer could be malfunctioning. Numerous times throughout the day the defrost timer should cycle the defrost heater on as a means to melt frost buildup on the evaporator coils in the freezer. If this timer does not cycle on, then it may be faulty and require replacement.
  1. Defrost heater assembly
If your refrigerator is not defrosting accurately this could be an indication that your defrost heater assembly has failed. This could cause the frost to accrue on the evaporator coils, eventually blocking the airflow resulting in the unit not cooling properly. The defrost heater assembly can be monitored for continuity using an ohm meter and will need to replaced if there is none present.
  1. Defrost thermostat
Another cause of your refrigerator not defrosting is a faulty defrost thermostat. A requirement for the defrost heater to activate to melt away frost on the evaporator coils is a functional defrost thermostat. The defrost thermostat senses the temperature of the evaporator coils and initiates the thawing process by activating the defrost heater. If the thermostat is faulty, it will not sense the lowering temperature of the coils and will not turn on the heater, resulting in an advanced frost build-up. The defrost thermostat can be checked for continuity by using an ohm meter; if there is no continuity the damaged part will need to be replaced.
  1. Defrost sensor with fuse
Another possible cause of a refrigerator that does not defrost properly is a defrost sensor with a fuse. If the defrost sensor fails, the fuse acts as a one-time-only fail safe for the sensor -- if the sensor does not shut off the defrost heater, the fuse will blow when the set temperature is reached. This safety precaution is to keep excessive harm from your unit by the heater and is a one-time use, resulting in the replacement of the entire defrost sensor.
Defrost drain problems
  1. Clogged or freezing defrost drain
If you are experiencing defrost drain issues, it is possibly due to a clogged or freezing drain that is blocking water flow to the bottom of the freezer. This will cause the defrost water to drain and drip down to the bottom of the freezer section. To correct this issue, thaw any ice or remove debris that could be causing the clogged drain or replace the drain heater.
  1. Drain heater
If you are experiencing defrost drain problems, inspect the defrost drain heater. A dislocated or burnt out drain heater will result in the drain tube freezing over. Attempt to return the part to the designated position or replace the damaged part to correct the issue. Search Over 2 1 Million Appliance Parts
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  1. Defrost control boardIf the defrost function is not working on your refrigerator it could be an issue with the defrost control board. This control board oversees several internal conditions and regulates the activation of the defrost cycle. A faulty board can be the primary reason your refrigeration unit is not transitioning to the defrost cycle. Over time, the buildup of ice on the evaporator coil will prevent the refrigerator and freezer from maintaining proper internal temperature. It is advisable to first check the defrost heater and the defrost thermostat for continuity prior to replacing the defrost control board.
  2. Main control boardA possible cause for a refrigerator not defrosting, especially on more modern units, is the main control board. The main control board acts as a "brain" for the unit controlling the defrost cycle, compressor, and run time, and essentially acts in place of the defrost timer. The control board can be tested using an ohm meter for functionality and will need to be replaced if bad.
  3. Defrost timerIf the refrigerator is not defrosting the timer could be malfunctioning. Numerous times throughout the day the defrost timer should cycle the defrost heater on as a means to melt frost buildup on the evaporator coils in the freezer. If this timer does not cycle on, then it may be faulty and require replacement.
  4. Defrost heater assemblyIf your refrigerator is not defrosting accurately this could be an indication that your defrost heater assembly has failed. This could cause the frost to accrue on the evaporator coils, eventually blocking the airflow resulting in the unit not cooling properly. The defrost heater assembly can be monitored for continuity using an ohm meter and will need to replaced if there is none present.
  5. Defrost thermostatAnother cause of your refrigerator not defrosting is a faulty defrost thermostat. A requirement for the defrost heater to activate to melt away frost on the evaporator coils is a functional defrost thermostat. The defrost thermostat senses the temperature of the evaporator coils and initiates the thawing process by activating the defrost heater. If the thermostat is faulty, it will not sense the lowering temperature of the coils and will not turn on the heater, resulting in an advanced frost build-up. The defrost thermostat can be checked for continuity by using an ohm meter; if there is no continuity the damaged part will need to be replaced.
  6. Defrost sensor with fuseAnother possible cause of a refrigerator that does not defrost properly is a defrost sensor with a fuse. If the defrost sensor fails, the fuse acts as a one-time-only fail safe for the sensor -- if the sensor does not shut off the defrost heater, the fuse will blow when the set temperature is reached. This safety precaution is to keep excessive harm from your unit by the heater and is a one-time use, resulting in the replacement of the entire defrost sensor.

Read more: http://www.appliancepartspros.com/repair-help/refrigerator-repair-help.html#9#ixzz2aX5nUL00
http://www.appliancepartspros.com
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The problem could be the electronic control if you have one or the mechanical linkages.

If the evaporator coils behind the back panel of the freezer are icing up because of auto defrost failure that will stop the circulation of cold air and eventually affect the freezer too.

check defrost timer, defrost heater, defrost thermostat. In most newer models the timer has been replaced by an electronic control board. If the heater and thermostat are ok it’ll be the control.

You can turn the defrost timer till it clicks and everything shuts down. The heater should now come on. If it does, replace the timer. If it doesn't, check the heater and defrost thermostat. Turn the timer again till everything starts back up to end the defrost cycle.


Your evaporator coils frost up in normal use and every eight hours or so the entire unit shuts down and the defrost heater comes on to melt the frost. This cycle last about 20 minutes. The melted frost drips into a drain pan and through a drain tube to the drain tray under the freezer/refrigerator where it's evaporated by the condenser fan.

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Your evaporator coils frost up in normal use and every eight hours or so the entire unit shuts down and the defrost heater comes on to melt the frost. This cycle last about 20 minutes. The melted frost drips into a drain pan and through a drain tube to the drain tray under the freezer/refrigerator where it's evaporated by the condenser fan.

If the evaporator coils behind the back panel of the freezer are icing up because of auto defrost failure that will stop the circulation of cold air

check defrost timer, defrost heater, defrost thermostat. In most newer models the timer has been replaced by an electronic control board. If the heater and thermostat are ok it’ll be the control.

You can turn the defrost timer till it clicks and everything shuts down. The heater should now come on. If it does, replace the timer. If it doesn't, check the heater and defrost thermostat. Turn the timer again till everything starts back up to end the defrost cycle.
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Your evaporator coils frost up in normal use and every eight hours or so the entire unit shuts down and the defrost heater comes on to melt the frost. This cycle last about 20 minutes. The melted frost drips into a drain pan and through a drain tube to the drain tray under the freezer/refrigerator where it's evaporated by the condenser fan.

If the evaporator coils behind the back panel of the freezer are icing up because of auto defrost failure that will stop the circulation of cold air and eventually affect the freezer too.

check defrost timer, defrost heater, defrost thermostat. In most newer models the timer has been replaced by an electronic control board. If the heater and thermostat are ok it’ll be the control.

You can turn the defrost timer till it clicks and everything shuts down. The heater should now come on. If it does, replace the timer. If it doesn't, check the heater and defrost thermostat. Turn the timer again till everything starts back up to end the defrost cycle.

How to check everything
http://www.acmehowto.com/howto/appliance/refrigerator/refrigerator.php




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How to check everything
http://www.acmehowto.com/howto/appliance/refrigerator/refrigerator.php

If the evaporator coils behind the back panel of the freezer are icing up because of auto defrost failure that will stop the circulation of cold air and eventually affect the freezer too.

check defrost timer, defrost heater, defrost thermostat. In most newer models the timer has been replaced by an electronic control board. If the heater and thermostat are ok it’ll be the control.

You can turn the defrost timer till it clicks and everything shuts down. The heater should now come on. If it does, replace the timer. If it doesn't, check the heater and defrost thermostat. Turn the timer again till everything starts back up to end the defrost cycle.


Your evaporator coils frost up in normal use and every eight hours or so the entire unit shuts down and the defrost heater comes on to melt the frost. This cycle last about 20 minutes. The melted frost drips into a drain pan and through a drain tube to the drain tray under the freezer/refrigerator where it's evaporated by the condenser fan.

Aug 22, 2009 • Freezers
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