Fridge kscs25fjss01 - Defrost heater doesn't get hot during test mode

Jeyeff, appreciate your detailed response! I made a mistake….I measured the heater again and it is 22 Ohms (not k). What do you think could be wrong at this point? I can’t find a defrost timer in this unit so maybe I should look into the main board?

Thank you again!

Hi @nelaco ,

I assume that you meant the bi-metal defrost thermostat when you said that you tested the defrost thermostat?

Go into test mode again and check if there is voltage being applied to the defrost heater in the defrost cycle.

Set up the meter first so that you only have to touch as little as possible (or even nothing) as the voltage supplied to the heater is at mains supply value so it can be lethal if you don't know what you're doing.

If there is no voltage turn off and disconnect the power before touching anything and then check the wiring from the mainboard to the heater with an Ohmmeter. You may have to trace the heater wire colours to find where they appear at the mainboard If that is OK it may be in the mainboard

Yes, I meant the bi-metal thermostat.

Ok, I'll disconnect the heater, then connect my volt meter, put it in test mode and then test the heater and see what/if voltage I get.

thank you again Jeyeff

Jeyeff, I went ahead and tested and I get NO voltage at all. I guess at this point the only solution is to replace the main board?

Thank you.

@nelaco ,

Did you prove the wiring between the heater and the control board or test for voltage where it leaves the control board to go to the heater, you didn't say?

I don't know the fridge but are there any relays on the control board that may be operated to send power to the heater?

If not it may be solid state switching which makes it difficult.

If you know where the heater wires connect to on the control board trace the tracks on the board (if possible) and see which components they lead to. Obviously you have to remove the control board to do this.

You may spot something.

With refrigerators in general during auto defrost the control board stops the compressor and evaporator fan and sends power to the heater.

The bi-metal defrost thermostat operates to signal the control board when the heater cut off temp has been reached i.e. ~32 - 33 F (this takes about 15- 20 minutes) to stop power to the heater so that the evaporator won't be damaged if the temp goes any higher and also to start the compressor again to end the auto defrost cycle and start cooling.

So since you have proven that the bi-metal defrost thermostat is OK and it is not telling the control board to stop the heater and presumably the compressor is stopped for long enough for the heater to have done its' job and for the defrost action to occur that just leaves the mainboard