Defrost Refrigerator Wiring Diagram

[Darth Sanderson]

HiChuck, I am in the process of restoring a similar 1966 GE ref with the same evaporator system and hot gas defrost. I in fact just used my last timer like I gave you guys for this project [ I bought these from Larry @ Modern Parts in Ohio back in 1999 ]

If you look closely at your old style defrost control you will see tinny #s next to the four terminals that are the same as on the new timer, the timer I supplied is the correct replacement defrost control for your refrigerator, Good Luck Hope this finally gets your ref working properly, John.

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?

@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)?

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.

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.

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.

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.

@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.

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.

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?

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.

I just want to clarify above specially the timer, that i had found mistake with due respect in the diagram. The timer here should be powered base on the specs, say 220V or 110V. Thus, terminals 1 and 3,which is the coil of the timer must be supplied with 220V or 110V. But in the schematic diagram above, the defrost timer will not work here because terminal 1 has no supply. Terminal 3 has already a line(red line-L), then terminal 1 should get a line from blue line (N). In the drawing above, you would expect that the terminal 1 would get a supply when the timer gets into defrost mode? Remember that during the defrost mode,terminal 3 will switch to terminal 2 that gives a supply to the heater. Now here, terminal 1 and 3 will share one supply during the defrost mode, which will turn into short circuit, but it will not gonna happen, the defrost timer here will not work because the other terminal has no power (terminal 1).

for type 1 circuit:

but the coil Timer has tolerance for about 10% for voltage drop. When it coil parallel with the Defrost Heater the voltage drop across Heater is very small, its about 2 volts drop in the Heater so the power supply to the timer coil approx. 218 volt or 108 volts in 110 volts circuit. The Timer still works properly. And when the Defrost Thermo bypass the timer coil, the Defrost Heater will get 220V or 110V and timer coil have no voltage between the two terminal (the Timer stop operation while system defrosted) and continue the time cycle when the Evaporator temperature reach the Defrost Thermo cut-in point/when all the ice form in the evaporator melted).

Terminal 1gain power from the blue line through the defrost heater while terminal 3 connected to terminal 4 to compressor.When the terminal 3 connected to terminal 2 in defrost mode timer will stop until the bimetal cut out.Most refrigerator japan made use this kind of wiring diagram. Europe or American made refrigerator use a different timer and wiring diagram.

In Saudi Arabia as well..I did repair many 110VAC no-frost Ref. Defrost timer should not stop, It is like a clock which has the defrost mode for 20 to 30 mins and advances then to cooling mode for 6 or 8 minutes, a cycle . When the defrost thermostat opens, it breaks the line going to the heater, then the heater will be off even the defrost mode is still going on.

You said the terminal 1 gains power from the blue line of the heater, defrost heater either 110 VAC or 220Vac must be supplied with power both its line 1 and line 2. The heater here has indicated a blue line (say Line1) and black (say line 2, will become red when the timer advances to defrost or to terminal 2), which is correct. Now the problem here is the defrost timer supply my friend. Look at it closely.

With the wiring error on our frig, most of this still worked the same. The difference was just that once the timer turned itself off, it was off for good, being quite thoroughly shorted out now by the direct connection between terminals 1 & 2, with no intervening defrost thermostat to bring it back to life at the proper time.

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temperature will colder than normal because the compressor continuous run until the defrost time reaches. for a long time, the liquid refrigerant will entering the compressor and damage the mechanical inside.

Its like you read my mind! You appear to know so much about this,

like you wrote the book in it or something.

I think that you could do with a few pics to drive the message home a bit,

but instead of that, this is great blog. A fantastic read.

I will certainly be back.

There are many separate components in a refrigerator's defrost system that must work in concert for a frost free system to work properly. We will attempt to explain the workings using simplified electrical schematics.

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