Bimetal defrost switch

Remove the panel. Check the heater and bimetal thermostat for continuity. If either is open then easy fix. Note: thermostat only has continuity if cold. When it gets over 50f it opens to kill power to the heater during the 20 minute defrost cycle.

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You didnt give the make of the ref.; But your solution is here for most all

The newest defrost feature in modern fridges is the electronic adaptive defrost control board. *Maytag has one version, see picture...to put this adaptive defrost style of fridge into defrost, short with a small screwdriver between L1 and test on the adaptive defrost board, wait 3 seconds and you should hear a "click" noise from the relay and the fridge will shut off and go through a defrost cycle. A close up common way *this* version of the Maytag/JennAir control is wired.
Amana also has a version of adaptive defrost, see info sheet for some help on the Amana version. Press refrigerator light switch five times in six seconds to initiate defrost cycle. Pressing five more times within six seconds will cancel defrost and go straight into the run mode. Similar operation on both bottom mount and SxS refrigerators. After the defrost terminator/thermostat opens, six minutes of dwell time occurs before the compressor and condenser fan motor will operate. After defrost terminator/thermostat open, 10 minutes of dwell time occurs before the evaporator fan motor will operate.
Frigidaire has also jumped into the market with an adaptive defrost board. The fresh food section light switch and light bulb must work. To initiate a defrost cycle, open the door and push the light switch in and out 5 times within 6 seconds. The compressor and fans should shut off and the defrost heater should come on. Open the door and push the light switch in and out 5 times within 6 seconds to remove the refrigerator from the defrost mode and back into a cooling mode.
Frigidaire - referance model FSC23F7DSB3
This product comes equipped with an Adaptive Defrost Control (ADC). To activate manual defrost, press and hold the Freezer temperature UP (WARMER) key while pressing the Fresh Food temperature DOWN (COLDER) key 5 times within 6 seconds. A ?¿½d?¿½ in the freezer temperature window and ?¿½F?¿½ in the refrigerator temperature window will display when the heater is activated. To deactivate manual defrost, press and hold Freezer temperature UP (WARMER) key while pressing the Fresh Food temperature DOWN (COLDER) key 5 times within 6 seconds. ?¿½d?¿½ and ?¿½F?¿½ will be displayed until the defrost cycle is complete. (approx. 8 minutes)
For some Whirlpool refrigerators - some Kenmore refrigerators are made by Whirlpool ( 106.######## )
The refrigerator/freezer defrost system can be checked by manually initiating a defrost cycle. There
are two methods of initiating the ADC Test Mode.
First Test Method:
1. Turn the thermostat off for 15 seconds.
2. Turn the thermostat on for 5 seconds.
3. Turn the thermostat off for 15 seconds.
4. Turn the thermostat on for 5 seconds.
5. Turn the thermostat off for 15 seconds.
6. Turn the thermostat on for 5 seconds.
7. Turn the thermostat off.
In 3 to 8 seconds the ADC should turn on the defrost heater (with the bimetal closed). NOTE: The test mode will terminate when the bimetal opens. If the refrigerator/freezer is already in defrost, Test Mode can be terminated by unplugging the refrigerator/freezer from the wall outlet and waiting 30 seconds before plugging it back in. The refrigerator/freezer should immediately go into cooling mode if the thermostat is closed.
If this first test procedure fails to make the ADC initiate a defrost cycle, try the following procedure to make the ADC begin the Test Mode.
Second Test Method:
1. Disconnect the refrigerator/freezer from the wall outlet for at least 30 seconds.
2. Turn the thermostat off.
3. Reconnect power to the refrigerator/freezer.
Within 3 to 8 seconds the ADC should turn on the defrost heater (with the bimetal close). If the unit fails to go into the defrost mode during this test, the problem may not be with the ADC. A defective bimetal may be the cause of the failure. The ADC will only go into a test mode if the bimetal
is closed. If the ADC senses an open bimetal it will return to the cooling mode within 3 to 8 seconds.
HELPFUL HINT: Upon entering the Test Mode, the relay mounted on the ADC board should turn off the compressor and turn on the defrost heater. Listen for the relay to click.
?¿½ If the relay clicks one time when entering the Test Mode, check for continuity in the defrost heater.
?¿½ If the relay clicks two times, check for an open bimetal.

Maytag S-S Refrigerator MSD2756GEW forcing defrost cycle
I replaced my defrost heater two weeks ago, but the frost built back up on the evaporator coils. Replaced the adaptive defrost board with new ( Maytag p/n 6100598 8 ) board. Want to force a defrost cycle to see the heater work, so I shorted the L1 pin to adjacent pin (now called DOOR instead of TEST) for three seconds and nothing happens. Compressor keeps running, fans still going etc. Tried pressing the door switches 5 times in 6 seconds and that doesn't work either. Any hints on how to get the defrost cycle to initiate?
Hi,
This might help, a copy:
The issue is that some 12002104 ADC boards have been shipped in the 61005988 ADC board box. Do not reorder the board, the 12002104 board will function the same in place of the 61005988, but you must use the forced defrost method for the 12002104. Jumping "L-1" and "door" will not initiate the forced defrost function.
To Initiate Forced Defrost Cycle:
Cycle cold control on and off three times in six seconds. The cold control needs to be left in the closed (call for cooling) position for the defrost system to energize on all platforms. It is not enough to cycle the cold control knob, the contacts must actually open and close (open doors for a period of time if necessary to force the control to call for cooling). In most cases, you can hear the contacts open and close if they are doing so.
To Terminate Forced Defrost Cycle:
Disconnect power for five seconds.
You were right. I cycled the cooling controls three times and it went into a defrost cycle. Thanks.

he refrigerator/freezer defrost system can be checked by manually initiating a defrost cycle. There
are two methods of initiating the ADC Test Mode.
First Test Method:
1. Turn the thermostat off for 15 seconds.
2. Turn the thermostat on for 5 seconds.
3. Turn the thermostat off for 15 seconds.
4. Turn the thermostat on for 5 seconds.
5. Turn the thermostat off for 15 seconds.
6. Turn the thermostat on for 5 seconds.
7. Turn the thermostat off.
In 3 to 8 seconds the ADC should turn on the defrost heater (with the bimetal closed). NOTE: The test mode will terminate when the bimetal opens. If the refrigerator/freezer is already in defrost, Test Mode can be terminated by unplugging the refrigerator/freezer from the wall outlet and waiting 30 seconds before plugging it back in. The refrigerator/freezer should immediately go into cooling mode if the thermostat is closed.
If this first test procedure fails to make the ADC initiate a defrost cycle, try the following procedure to make the ADC begin the Test Mode.
Second Test Method:
1. Disconnect the refrigerator/freezer from the wall outlet for at least 30 seconds.
2. Turn the thermostat off.
3. Reconnect power to the refrigerator/freezer.
Within 3 to 8 seconds the ADC should turn on the defrost heater (with the bimetal close). If the unit fails to go into the defrost mode during this test, the problem may not be with the ADC. A defective bimetal may be the cause of the failure. The ADC will only go into a test mode if the bimetal
is closed. If the ADC senses an open bimetal it will return to the cooling mode within 3 to 8 seconds.
HELPFUL HINT: Upon entering the Test Mode, the relay mounted on the ADC board should turn off the compressor and turn on the defrost heater. Listen for the relay to click.
• If the relay clicks one time when entering the Test Mode, check for continuity in the defrost heater.
• If the relay clicks two times, check for an open bimetal.

Hello,

Sounds like you have a defrost problem since the freezer side is working okay . It probably is not blowing cold air into the refrigerator side , so to check the defrost circuit , unplug the refrigerator and inside the refrigerator section at the top about 2" in from each side in the back , there are "D" slots to put a finger in , and pull downward and forward , to remove the control panel cover . Once removed , there is a 1/4" screw on each side holding the adjustment indicator panel on , 1 Phillips screw behind both light bulbs , and 1 screw holding the complete panel to the rear wall . After removing these 5 screws , at the top right corner , with about 6-8 wires going to it , is the adaptive defrost board . Sometimes you can see the electronic board and on newer refrigerator's , a white box will be seen. Inside this box , is the adaptive defrost control . Disconnect the plug going to the board and on the right side of the PLUG , the far right wire is yellow , then another color , then white . Using a small insulated wire with both ends stripped , insert one end into the yellow wire hole and the other into the white wire hole . This will bypass the adaptive board and send power directly through the defrost bimetal ( thermostat ) AND heater to check if they are good .Plug the refrigerator back in . Now , wait about 3-5 min and look for a red glow at the bottom of the inside freezer panel , which will be the defrost heater or listen for sizzling which will be the frost melting and dripping onto the heater .If NO red glow , watch for a spark while removing the jumper wire you installed , from the plug . If a spark IS seen , then the heater was on and the heater AND bimetal are good . If you see the red glow , hear the sizzling , or see the spark , then the adaptive defrost board should be replaced . If no glow , sizzling or spark , then unplug the refrigerator and reinstall the refrigerator control section .
Remove the food in the freezer section enough so that the 2 screws holding the lower freezer panel on and the freezer panel , can be removed . Remove the panel . If the heater (black element at the bottom of the coils ) wires are visible , trace then to the top of the coils and disconnect . Use an ohm meter to determine if the element is good . If the element IS good , at the top of the coils , is a 1" cylinder with 2 wires , clipped onto the coils . This is the defrost thermostat ( bimetal ) . Replace this part if the element shows good . If the element shows bad , replace the element . NOTE 1 : sometimes the element and the bimetal come wired together and the replacement part comes with a new heater and bimetal already wired together . This would be the adviseable replacement part . However , each part can still be replaced individually . NOTE 2 : If looking at the bimetal and the top plastic " cap " looks cockeyed , replace the bimetal as moisture has gotten inside and disturbed its designed function .

I hope this will help in solving the problem....

The refrigerator/freezer defrost system can be checked by manually initiating a defrost cycle. There
are two methods of initiating the ADC Test Mode.
First Test Method:
1. Turn the thermostat off for 15 seconds.
2. Turn the thermostat on for 5 seconds.
3. Turn the thermostat off for 15 seconds.
4. Turn the thermostat on for 5 seconds.
5. Turn the thermostat off for 15 seconds.
6. Turn the thermostat on for 5 seconds.
7. Turn the thermostat off.
In 3 to 8 seconds the ADC should turn on the defrost heater (with the bimetal closed). NOTE: The test mode will terminate when the bimetal opens. If the refrigerator/freezer is already in defrost, Test Mode can be terminated by unplugging the refrigerator/freezer from the wall outlet and waiting 30 seconds before plugging it back in. The refrigerator/freezer should immediately go into cooling mode if the thermostat is closed.
If this first test procedure fails to make the ADC initiate a defrost cycle, try the following procedure to make the ADC begin the Test Mode.
Second Test Method:
1. Disconnect the refrigerator/freezer from the wall outlet for at least 30 seconds.
2. Turn the thermostat off.
3. Reconnect power to the refrigerator/freezer.
Within 3 to 8 seconds the ADC should turn on the defrost heater (with the bimetal close). If the unit fails to go into the defrost mode during this test, the problem may not be with the ADC. A defective bimetal may be the cause of the failure. The ADC will only go into a test mode if the bimetal
is closed. If the ADC senses an open bimetal it will return to the cooling mode within 3 to 8 seconds.
HELPFUL HINT: Upon entering the Test Mode, the relay mounted on the ADC board should turn off the compressor and turn on the defrost heater. Listen for the relay to click.
• If the relay clicks one time when entering the Test Mode, check for continuity in the defrost heater.
• If the relay clicks two times, check for an open bimetal.

IF the evaporator is frozen then the defrost is not occuring. Probably the heater or the defrost thermostat.

Change out the defrost timer and defrost bimetal in the freezer. If yours is controlled by a control board then change the board and the bimetal thermostat in the freezer

Replace the defrost thermostat , not the motor . The defrost thermostat ( bimetal ) sends power to the fan motor when bimetal is cold ( 35 degrees maybe ) . When first plugged in , the compressor cools the coils until the bimetal clicks on . Then the fan comes on , blowing cold air into the fridge . If the fan came on when first plugged in , it would blow warm air , gradually getting colder . Amana is the only brand using this process of coolant .

The refrigerator/freezer defrost system can be checked by manually initiating a defrost cycle. There
are two methods of initiating the ADC Test Mode.
First Test Method:
1. Turn the thermostat off for 15 seconds.
2. Turn the thermostat on for 5 seconds.
3. Turn the thermostat off for 15 seconds.
4. Turn the thermostat on for 5 seconds.
5. Turn the thermostat off for 15 seconds.
6. Turn the thermostat on for 5 seconds.
7. Turn the thermostat off.
In 3 to 8 seconds the ADC should turn on the defrost heater (with the bimetal closed). NOTE: The test mode will terminate when the bimetal opens. If the refrigerator/freezer is already in defrost, Test Mode can be terminated by unplugging the refrigerator/freezer from the wall outlet and waiting 30 seconds before plugging it back in. The refrigerator/freezer should immediately go into cooling mode if the thermostat is closed.
If this first test procedure fails to make the ADC initiate a defrost cycle, try the following procedure to make the ADC begin the Test Mode.
Second Test Method:
1. Disconnect the refrigerator/freezer from the wall outlet for at least 30 seconds.
2. Turn the thermostat off.
3. Reconnect power to the refrigerator/freezer.
Within 3 to 8 seconds the ADC should turn on the defrost heater (with the bimetal close). If the unit fails to go into the defrost mode during this test, the problem may not be with the ADC. A defective bimetal may be the cause of the failure. The ADC will only go into a test mode if the bimetal
is closed. If the ADC senses an open bimetal it will return to the cooling mode within 3 to 8 seconds. 
HELPFUL HINT: Upon entering the Test Mode, the relay mounted on the ADC board should turn off the compressor and turn on the defrost heater. Listen for the relay to click.
� If the relay clicks one time when entering the Test Mode, check for continuity in the defrost heater.
� If the relay clicks two times, check for an open bimetal.

Hi. I reccommend you replace the defrost timer and bimetal thermostat. The bimetal thermostat is located on the evaporator coil. The bimetal thermostat is the most common failure. Good luck, Mack