Electric Dryer Wiring Diagram For Whirlpool Dryer Heating Element – We haven’t fixed anything in a while. But don’t worry – there’s always something breaking here! Recently, our fancy electric dryer decided to stop using it.
The symptoms are typical and have been described all over the web: the power button has no response, some LEDs glow dimly, and the interior bulb turns on when the door is opened. Sometimes, I can make it work by turning off the dryer circuit breaker and letting it sit for a few days. Yes, very popular with SWMBO. Solutions are all over the place, mostly suggesting replacing the control board ($250), user interface panel ($145), or thermal fuse ($12). The problem is, you first need to know what you actually want and debug.
Electric Dryer Wiring Diagram For Whirlpool Dryer Heating Element
Removing the skirting boards yields a bag with a repair manual and schematics – very handy. However, it turns out that the thermal fuse is perfectly fine. Well then.
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Disassembling the unit is very easy – unscrew the three screws on the back, slide the top cover off and the control board is on the left side for easy reach. Looking at the schematics, there’s not much to stop the thing from opening.
A light on means we have 120V. Checking the terminals on the control board also confirmed this. Now it depends on the board or UI. I removed both (which included some screws and disconnecting some connectors) and put them on the bench to debug. Fortunately, I was able to fail it in Workbench – a very important step in any debug:
The system still refused to see any key presses, so I started messing around with the oscilloscope. The whole thing runs on Freescale Micro co-branded with Whirlpool and comes in a giant DIP package. 5V power and reset looks good, there is definitely activity on the IO – I can see the micro scan pad wires.
Looking at the number of LEDs and buttons, it is quickly apparent that some major multiplexing is used. There isn’t enough signal to drive everything directly through the 14 and 6 pin cables between the boards. They have three dedicated inputs for special function buttons – power on, start, etc. Two of them have different waveforms than the third. (Just to boot!). Well, go somewhere.
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So I looked around and couldn’t see any clearly defective components. I replaced the cables between the boards with individual wires and tried removing them one by one to see if the problem persists. I went ahead and re-soldered all the connectors between the two boards, but nothing changed. As I was sitting there looking at things and trying to picture how the whole mess of multiplexing works, I happened to notice that one of the LEDs (I think it was the D15, Wrinkle Guard) and the other lights were dim lights. blinking
I plugged it back in and the light went off but the system booted. Of course, the scan signal on the power-on button now matches the other two. Interesting! So I closed the board and re-soldered all the LEDs on the entire front interface assembly.
Power cycled and everything worked fine. I ran the built-in diagnostics and all the LEDs came on normally:
It’s been a few months since the repair and the dryer is still starting every time. I’m too lazy to trace exactly what the designers multiplexed together, but it looks like they’re using reverse biased LEDs as diodes in the scan matrix. So the off LED can still affect things, a bad solder joint in the far corner of the board to stop the seemingly unrelated power button from working.
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If you try this yourself, make sure you know what you’re doing, always disconnect and do so at your own risk. There is high voltage in the dryer! This article schematically shows where voltages appear in a whirlpool dryer circuit for various operating modes and fault conditions. This information is useful for technicians who want to use voltage checks in addition to other troubleshooting methods. Note that this article is intended for experienced equipment technicians only. Please do not work on live circuits unless you are qualified and take proper safety precautions.
With the dryer plugged into a 240V outlet, you can see the voltage paths below, where black is L1, red is L2, and blue is neutral. L1 and L2 are 240V to each other. L1 and L2 120V with respect to neutral, but opposite polarity.
The timer has now advanced to Air Fluff mode and the dryer has not started. L1 goes through the motor windings to the left of the start switch. The neutral wire is still to the right of the start switch, but now continues through timer contacts TM and WB to the right of the timer, which now has 120V across it.
As the timer advances to the drying time, the voltage path changes when the timer connects BK and R so that L1 passes through all elements to the bottom of the centrifugal switch of the motor. There is no voltage drop in any of these components because the circuit is not closed and therefore no current flows.
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When the start switch is pressed but not fast enough to trip the centrifugal switch, the voltage will be as shown below. Note that full 120V is visible to the motor through L1 on the left and the start and main windings. At this point, the start winding gives some phase-shifted orientation relative to the main winding to start the motor spinning. At this time, since the centrifugal switch is not tripped, the voltage on the thermal circuit side of the centrifugal switch is still 240V and no current flows through the heating element.
Once the centrifugal switch moves to about 3/4 full motor speed, the start winding is no longer energized as shown below. The momentum of the motor and the 180-degree north-south shift of the main winding each half cycle make the motor rotate. Note that the centrifugal switch is now closed with 0V across it, current flows through the heating circuit and the heating element is powered by the 240V difference between L1 and L2.
In this particular model, the auto-dry feature only advances the timer when the element is cycled off by the thermostat. When the element is turned on, the timer stops progressing. This is achieved by feeding L2 through a resistor to the right of the timer. However, when the element is turned on, the voltage is displayed as below and the timer has no voltage.
When the element is turned off, 240V appears across the cycling thermostat because L2 goes straight through the element and to the right of the resistor – then 120V drops across the resistor – leaving 120V for the timer relative to the right side of L1. The timer now continues until the cycling thermostat closes – and the cycle repeats.
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The remaining figures show common faults and associated voltage paths for this dryer. During automatic drying, if the wire connecting the heating element to the timer breaks, the dryer will run continuously – cycling the heat on and off until the timer is manually advanced by the user.
Next, in auto-dry mode, the element is open or shorted, L2 is no longer visible on the left side of the element and no longer provides voltage to the right side of the timer motor through the resistor. Consumers have complained that the dryer runs forever without heat in auto dry mode or on the cool side with timed drying.
Second, a common feature of this type of dryer is the lack of heat. The following voltage diagram shows what happens if the BK – R timer connections fail. This is a common cause because a lot of current flows through these contacts – generating a lot of heat – which hastens their failure.
A voltage graph follows with the same symptoms – no heat, faulty centrifugal thermal circuit switch. In this case, the centrifugal switch of the thermal circuit is not closed and 240 V is still present. No voltage appears on the right side of the element and no current flows. You can easily check this by checking the voltage from L2 to the element – if you’re getting 240V, your centrifugal switch – and thus your motor – has failed.
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Another common symptom is that the dryer won’t start. This is usually caused by a thermal fuse. If so, your voltage will look like this. You can measure BK and
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