Where is the defrost control unit and how do I get to it

Usually every 6 hours will keep the evaporator coil clear of frost. I set the time at 45 minutes per defrost. This unit has a defrost termination control that kicks it out of defrost when the coil reaches a certain temperature. The defrost timer is only a backup if the defrost control fails.

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

dont worry about it, you probably didnt get the freezer drawer closed all the way. frost will form when it doesnt get closed properly. just make sure it is closed now and the unit will clear the frost in a few days thru normal defrosting cycles. be sure that the drawer is closing on all sides by looking at the gasket and all should be ok in the future.

test this steps and fix it, use the VOM. God bless you

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

Hi and welcome to FixYa, I am Kelly.
This is an automatic defrosting problem. You can get few days (2 - 3) of normal temps by doing a manual defrost. Unplug the unit..empty the freezer contents and direct and external fan into the freezer compartment for just over 2 hours while it makes a water mess. (Mop ready!) Then plug the unit back in. It will operate normally for 2 to 3 days before icing up again due to the automatic defrosting system problem you currently have.

There are 3 components that can cause the problem:
1. Defrost control Item 13 this link:
http://www.appliancepartspros.com/partsearch/model.aspx?model_id=47966&diagram_id=28494314#d28494314
2. Defrost Heating Element Item 12 this link:
http://www.appliancepartspros.com/partsearch/model.aspx?model_id=47966&diagram_id=28494316#d28494316
3. Defrost thermostat or thermistor (depending on model) Resistance is measured for 240 K ohms above 60 deg F and lower resistance below 60 F. It is part of the defrost heater assembly item 12 above. (Line 2)
Detailed view of the defrost heater and thermostat is here:
http://www.appliancepartspros.com/Appliance-Parts/whirlpool-defrost-heater-assembly-item-number-ap4069923.aspx

The wiring diagram is here:
http://www.appliancepartspros.com/partsearch/frame_diagram.aspx?diagram_id=28494324&pkw_=basket&model_id=47966&NewWindow=1
You can test the defrost heater by reading the Yellow wire to White / Black on the adaptive defrost control board. (unit unplugged)
The thermostat can be tested by making sure the temp control is on / unit should be in a it should be running situation BUT the unit is UNPLUGGED / below 60 F ... then read the Red wire to the White / Black wire at the adaptive defrost control for Very low resistance.
If the Defrost heater and thermostat check out fine... then the problem is the adaptive defrost control.
Just a note.....about powering up;. Once the unit is unplugged you must wait 15 minutes before re-powering the unit so the coolant system will stabilize and the compressor will start normally.
That is pretty much the basics of troubleshooting to identify the failure.
Thanks for choosing FixYa,
Kelly

Change the defrost control.

Hi and welcome ti FixYa, I am Kelly.
Since you did not include your model number this will be a GENERIC response.

Reasons for the compressor and fan not to run.

1. Defrost control problem. Mechanical defrost timer stuck or failure. On units with Electronic Adaptive Defrost controls; a PCB failure.

2. Defrost thermostat or defrost heating element failure.

3. Fresh Food temp. control failure.

These are the 3 most common failures. The fans should run anytime the units temp control is above the "set temp" and the unit is NOT in the automatic defrosting cycle.

If you provide a model number I can pass on some troubleshooting tips to hopefully help you isolate the failed componenet.

Thanks for choosing FixYa,
Kelly

There is definately a ground fault in this unit. Also according to the service manual this is an "Electronic Defrost Control" similar to an "
Adaptive Defrost Control" which determins the defrost initiation by the amount of run time. You cannot set this yourself.

If the heater ohms out fine and you have continuity and you have replaced the defrost thermostat then the only other issue would be your defrost control. Depending on the age of the unit it may just have a timer style defrost control or an adaptive control board. The thermostat would be located at the top of the evaporator coils. Defrost controls are probably the least likely of the system to fail. Usually when they do the unit sticks in defrost and the unit will be totally dead. If its a dial style timer you can advance it with a flat head screwdriver until it clicks this should send power to the defrost heater. Hope this helps _MJ_

The unit was built bt LG. It is a computer controled unit and the timer is built into the main control board on back of the unit. However, the most likely cause of the broblem is the defrost terminator located on the evap on the upper right hand corner. Also, try unpugging the unit it will reset the computer board. You will also have to defrost the unit.