I have a defrost cycle problem with my Kitchen Aid refrigerator. It is a model KTRC19MKSS00. The condenser is frosting up about every two days. I have had it apart several times trying to resolve this trouble. This model has an electronic defrost control board that operates the defrost as well as the cooling cycles. It has on the board a relay that is a SPDT. When released it applies 115vac to the cooling circuit and when operated it removes power from the cooling circuit and supplies power to the defrost circuit. The defroster element is supplied power from this board through a bi-metal. On the control board is two test terminals that are electrically connected to either side of the bi-metal. I can force the defrost cycle to initiate per the instructions on my service and wiring sheet #2213196REL. There is a helpful hint on the service sheet that indicates a possible open bi-metal if the relay operates and then releases within about 30 seconds into the defrost cycle. This is happening on my test. I have tested the bi-metal and it has less than one ohm across the terminals. As a precaution I have replaced the bi-metal. I am still having the same trouble condition. I have been able to jumper across the test terminals on the control board, thus bypassing the bi-metal and the defrost cycle runs the complete 18 minutes. I don't have enough detail information on the wiring diagram to troubleshoot the control board but I am wondering if it may have a trouble causing the relay to release prematurely. I'm trying to avoid buying a control board until I'm sure that is the trouble. What suggestions might anyone have?

Hi,

Evaporator.
Condensor is the hot tubing.

If the defrost thermostat/bimetal checks ok, heater ohms/checks ok....the bimetal should be ok since it is new....the board is normally automatically changed out.

Defrost control board

jeff.

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Jeff,

You are correct. I'm sorry about the error on my post. We are talking about the evaporator instead of the condenser. I know electronics pretty well but very little about refrigeration. Thanks for the input. I'll order the board directly. I had pretty much eliminated the other possibilities for the trouble but needed a little encouragement. I wish I had a diagram of the electronic control board for the defroster. I would like to know logically why the board worked when the bi-metal was bypassed with the jumper and wouldn't work through the bi-metal even though it's resistance was less than one ohm when operated. One thing I did discover during my career in electronics was that logic circuits don't always behave logically! Thanks again for the advice.

Mike

jeff.

__________________
http://www.applianceaid.com/
Appliance Repair Aid
http://www.jrappliance.ca
JRAppliance

After 8 months of manually defrosting my freezer as I tried to find this trouble, it's finally fixed. I eventually replaced the ADC as someone had suggested. I was hesitant as the unit was expensive. My resolve was well deserved as this did not fix the problem. I managed to get some additional information on a website about the ADC (automatic defrost control) board. I found out that is was an adaptive defrost control board that has a microprocessor in it. This control board monitors information from several locations to determine the time elapsed between defrost cycles. There is a brown lead that on one end attaches between the defrost thermostat and the defrost heater. The other end is attached to the ADC at one of the monitor terminals. The ADC is in the refrigerator section and the defrost components are in the freezer section. They are connected together through a harness and connectors on each end. This harness is put in place at the factory and foam is injected between the inside and outside shell of the refrigerator. It is not accessible. After several trouble shooting attempts, I found that the brown lead in the harness was going open momentarily. This made the ADC think that the defrost thermostat had opened, consequently the ADC removed the voltage to the defrost circuit. I had to bypass the harness and run a wire from the defrost thermostat/defrost heater connect point to the ADC monitor lead point through the return vent between the refrigerator/freezer sections. This has fixed the trouble and all is working well.

Mike