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Repair information, service manuals, and troubleshooting help for refrigerators manufactured by KitchenAid.

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whenever it goes into defrost mode, it turns the lights off

I have a Kitchenaid (model ktrp20khbt00) and whenever it goes into defrost mode, it turns the lights (in freezer and refrigerator) off and it doesn't even perform the defrost. I've changed the defrost timer and it is still doing the exact same thing. Now I have ice building up every 2-4 days and no lights. If it's not the timer, what else could it be?

Update (09/19/23)

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@jayeff I did hire a service tech and he's been here 5x in the last 2 months and still cannot fix it. The last time he was here, he took out the defrost timer and put in some sort of loop to make the light and icemaker work, which obviously causes the ice to build up. I have since put back the defrost timer and we're back to square one. What I can't figure out is where do the two wires in the front go (the brown and pink wires coming from the defrost timer connection)?

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Hi @thuyledinh

The lights in both the freezer and the refrigerator compartments are controlled by their associated door switch.

If they don't turn on at all whenever the appropriate door is opened, then it is either a door switch problem or a wiring problem to the switches or the lamps.

Regarding the no defrost problem, if it goes into the defrost mode and the ice on the evaporator unit isn't being melted it could be a faulty defrost heater or a faulty bi-metal defrost thermostat.

Disconnect the power to the refrigerator and then unplug the defrost heater- part #WP2315530 (supplier example only) which is located under the evaporator unit, from the wiring harness and use an Ohmmeter to test it for continuity. I don't know what its resistance value is but it shouldn't test open circuit.

If the heater is OK, here's a video that shows how to test a bi-metal defrost thermostat -part #WP4387503 (supplier example only). The defrost thermostat is also located near to the evaporator unit inside the freezer compartment.

Here's the tech sheet for the refrigerator that has the wiring diagram. Both the full detailed schematic and the simplified version that may also help, especially if it is a wiring problem with the lights.

If a part is faulty and needs replacing, search online using the part number only to find suppliers that suit you best.

Update (09/20/23)

Hi @thuyledinh

That end of the brown and pink wires go nowhere. They are test points as shown in the wiring diagram. The other end of the wires go to the defrost timer - bi-metal defrost thermostat connection and the bi-metal defrost thermostat - heater connection - see image below.

How to read a wiring diagram 101.

In the image are two more images that shows the power path for:

green arrows - normal operation show all the components that receive power during normal operation

red arrows - defrost cycle show all the components that receive power during the defrost cycle

Normal operation

The power to the defrost timer motor, compressor motor, evaporator fan motor and condenser fan motor is controlled the temperature thermostat.

The power to the compressor motor, evaporator fan motor and condenser fan motor is also controlled by the defrost timer thermostat.

The temperature thermostat opens when the correct temperature is reached and this stops the defrost timer motor, compressor motor, evaporator fan motor and condenser fan motor from operating. When the temperature in the compartments warms up, the thermostat closes and reconnects power to the defrost timer motor, compressor motor, evaporator fan motor and condenser fan motor and they start to operate again.

So the temperature is controlled by the thermostat turning the compressor, fans etc on and off to keep the temp within the set limits.

Defrost cycle:

When the defrost timer has operated for a cumulative compressor run time of 8-10 hours the defrost timer contacts switch over and disconnect power to the compressor motor, evaporator fan motor and condenser fan motor and connect power to the defrost heater.

The bi-metal thermostat in the heater path is a safeguard to prevent the evaporator unit from getting too hot and damaging it. It is only thin Aluminium and can be easily damaged by excessive heat from the heater which is directly beneath it. If the temp gets too hot the bi-metal thermostat operates and disconnects the heater. When the temp cools down again it releases and allows the heater circuit to be ready for the next defrost cycle.

The defrost timer motor continues to operate and when the set time for the defrost cycle has elapsed, the contacts switch back and disconnect the power to the defrost heater and connect power again to the compressor motor, evaporator fan motor and condenser fan motor turning them on to get the refrigerator back into normal operation.

At all times the lights and ice maker have power available. It is not controlled by the defrost timer or the thermostat.

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This is very helpful, going to try these suggestions, thank you.


@jayeff, so I changed the defrost timer and the bi-metal defrost thermostat and the problem still persist. Actually, when the timer switches to defrost mode it shuts the lights and icemaker down. Therefore, when I manually move it out of defrost mode, the lights and icemaker starts to work again. Could it be that the defrost heater is causing a short and shuts everything else off? The heater element is the only thing I have not yet changed. Let me know if you have any ideas, it's becoming quite a puzzle here and I'm stumped.



I did suggest that you test the defrost heater in my answer above to make sure it it was OK or not.

The same with the door switches for the lights

I'm surprised that you haven't already done this.

If the lights and ice maker turn off when the defrost mode is on then something is shunting the voltage.

Looking at the tech sheet wiring diagram, the timer should have no effect on the lights or the ice maker as they are connected in parallel with the timer so there should always be power connected to them -see the simplified wiring diagram on the right side of the page of the tech sheet at the bottom.

The lights and ice maker are connected directly to the power and not via anything else


Hi @jayeff, yes, you are correct and I would have tested it but I honestly wouldn't know how to do that or read the schema (or understand it) as I'm just a homeowner and not a technician. It was easier to replace parts as I can get instructions online on how to do those things. Having said that, when you say something is shunting the voltage when in defrost mode, what could be causing that? It's likely be a number of things, but where would you start to look?


Hi @thuyledinh

To test you would have to be dealing with exposed potentially lethal AC voltage to check what is happening so I would rather not try to explain how to do this mainly for your safety and my peace of mind.

The power should NOT be missing from the ice maker or the lights just because a defrost cycle is happening, so if it is then either there's a wiring problem or if something was shunting the voltage down (and you would have to measure this to know and this is dangerous if you don't know how to test lethal AC voltage safely) then if it were and there was excess current flowing because of this why isn't the house fuse blowing (or breaker tripping) or is it just too low for the lights not to even glow (which is strange) and not blow the fuse.

It may be easier to keep replacing parts but if it is a wiring problem then replacing parts won't fix it and you've spent a lot trying to fix it and it is still not fixed. In the end getting a repair service in to fix it might have been cheaper.


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Thuy LeDinh zal eeuwig dankbaar zijn.

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