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Electric Dryer Only Runs on Heat Cycles -- Solved with Schematic-Fu!


Son of Samurai

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We've got a tricky one for you today: a Frigidaire-built Kenmore electric dryer that only runs on heat cycles. If you set it to a timed or auto dry, it runs just fine. But set it to air fluff, and you get nada -- no motor rotation, no nothin'. Sounds like a bad timer, right? That was our first thought, too. But like any good tech should, we covered all of our bases before jumping to conclusions, and what we found was much more interesting...

We'll start by analyzing the circuit of the motor, since that's the LOI -- the thing that ain't doing its thang.

804448707_134061500eDriveMotorCircuit.png.425e3e4be9348f97afcebda14667a0da.png

And the timer chart as well, paying special attention to B-C, since those are the contacts that need to close for the motor to run in both timed dry and air fluff.

134061500e_pdf.png.aa92eac798e5e669362a49d4dd038ad1.png

Looks pretty standard, and what's more, it looks like B-C really is the only possible culprit. A quick and dirty test that can tell us for sure if B-C is staying open in air fluff would be to run an air fluff cycle, then jump B-C, bypassing the timer. If that makes the motor run, then that would prove it's a problem with the timer not closing B-C in air fluff.

So what happens when you perform that test in this scenario? Nothing. Jumping B-C makes no difference.

Boy, that's a real head-scratcher. Fortunately, just as we were at a loss, a new piece of info came to light: a couple of wires had been clipped out of a molex connector and spliced together. Specifically, we're looking at the red wire going to B on the timer, and the orange wire going to A.

With this new revelation, it all became clear. The red wire and the orange wire had been incorrectly spliced together. Not sure what the implications of that are? Neither were we, until we sat down and sketched it out on a schematic.

Kenmore_417_83042201_Dryer_Motor_no-run_in_air_fluff_cycle.png.813d8a137c316bdd608393289a0cbed3.png

And now our problem statement finally makes sense. With this incorrect splice, L1 could only make it to contact C of the timer if contact A was closed, which only happens during a heat cycle.

There we have it -- our definitive answer to what caused this problem. No guesswork, no Hail Mary part swaps. Once that splice was corrected, things started working just as they should.

Want to learn to understand circuits and troubleshoot like a pro? Click here to enroll in the online Core Appliance Repair Training course over at the Master Samurai Tech Academy.

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Did the customer own up to messing with it or could it have been a previous appliance repair person who made the splice blunder? 

Charlie

 

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  • Team Samurai
39 minutes ago, Chashb said:

Did the customer own up to messing with it or could it have been a previous appliance repair person who made the splice blunder? 

This scenario was taken from a repair topic here on Appliantology, and I believe in that case, it was a previous tech who had made the wonky splice.

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msaylor@mrapplianceofphx.com

Posted

A couple of missing items of interest:

Did a tech. splice the wires?

If so why? It must have worked after putting the wiring back to the factory wiring...!

Thanks,

Mark

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  • Team Samurai
1 hour ago, msaylor@mrapplianceofphx.com said:

Did a tech. splice the wires?

If so why? It must have worked after putting the wiring back to the factory wiring...!

Yes, a tech did make the splice, and best we can figure, it was because a hot connection had burned the molex connector that the wires were originally a part of.

And yes, it did work correctly once the wiring had been corrected.

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B-C control both motor and heater ( Schematic #1). Red - Orange ( Schematic # 2) , If M1 and M2 welded the heater stays ON by itself...fire hazard.

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  • Team Samurai
33 minutes ago, beyerappliance said:

B-C control both motor and heater ( Schematic #1).

I'm uncertain exactly what you're saying here. In the circuit as intended by the manufacturer, which is what's shown in the first schematic, B-C only controls the power supply to the motor. The heater circuit has its own timer contact: B-A.

Does that clarify things, or am I misunderstanding the point you were making?

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Thanks for the breakdown, these are situations where spending time to truly understand the problem is the difference between guessing and knowing.

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