Kenmore dryer stops too soon early


I have a seven year old Kenmore electric dryer (110.66702690) that stops drying mid-cycle. It only does this when it is set on Auto Dry I heat settings (Auto Dry I is where it uses a thermostat on the exhaust to determine when the clothes are dry). It just takes pushing the "Start switch" to start the dryer back up again (if only for a few minutes). It goes full cycle on the Timed Dry cycle.
I scanned in the wiring diagram that was in the dryers console:     
http://www.ddktech.com/schematic.jpg
Now, normally, when the thermostat (in red) senses dry air (and hence dry clothes), the heater should shutdown, but the drive motor should still spin. The thermostat doesn't control the motor, so I don't suspect the thermostat. However, last spring, a bird nested in the dryer's exhaust pipe outside the house. About 2 weeks went by before my wife told me about the clothes not drying before I was able to clear out the nest.
The centrifugal switch (in blue) in the motor should be independent of which cycle is selected.
The thermal fuse (in yellow) is described as being "not resettable", which I think would describe a fuse similar to car fuses or old house fuses. So if something were wrong with it, then the motor should not spin at all.
I've seen other posts recommend the timer itself as being the problem. I don't really believe that can be my problem. The dryer fails on both the "Perm. Press" and "Knit Delicate" phases of the "Auto Dry I" setting. It never stops on the "Timed Dry" or "Air Dry". If it was the timer, I don't think pushing the "Start switch" would start it up again. However, I can't eliminate it as the problem due it controlling so much in the dryer. And I would rather only replace it if I knew it *is* the problem as Kenmore's replacement part is $75.
I'm at a loss in determining what the problem really is. I would appreciate any help anyone could give.
Daniel
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Daniel S. Schudel
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If my sales training was right, the thermostat on the exhaust doesn't actually sense "dry" clothes. The auto 1 cycle works this way....As the heat comes on and is rising, the timer doesn't advance, when the heat cycles off at it's upper limit setting, the timer will start to advance but as the clothes are wet, it won't get far before the heat cycles on again and stops its forward motion. This cycle continues repeating itself but as the clothes get dryer, they don't cool the inside of the dryer so fast and the timer is allowed to advance further each time of "heat off" and subsequently runs the timer out and shuts off. If all is well this coincides with the clothes being dry. But if it isn't cycling the timer off, it would run out before the clothes were dry. However, I read you to say that the timer is still in the middle of its "on" position as all you have to do is hit the start button so it must not be running to the end prematurely. I'm not a service person so I'm sure I haven't been of much help. And I'm not all that familiar with how electricity works (other than I don't stick my finger in any light sockets) but I have a question. What is the function of the resistor in the auto dry cycle line just to the right of the switch. If that were defective, could it somehow open (or close, whatever they do) and stop the heater coil and motor. And one other question...re: the thermal fuse...does "not resettable" mean that it could burn out and not be resettable like a circuit breaker or does it mean that you can't adjust the heat limit at which it cuts out but that it closes back up automatically when cooled down some? Geez, I think I had more questions than you did... Tom.
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Thanks for the detailed description.

I can see that affecting the heater element and the timer motor. If the resistor was the cause, I have the feeling that the drive motor would still spin and perhaps the clothes would not dry.

Be sure and read one of the follow up messages psted by Jeff regarding the fuse.

Sometimes questions are more helpful than answers.
Thanks Tom, Daniel
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Hi,

The motors built in safety can do this, but -usually- needs a bit of cooling down time before going again. Loose/burnt main power wire ( inside the dryer or in house feed ), door switch, door switch bracket, timer ( broken/shifted cam inside the timer ), belt broken switch ( didn't see one on your model ).

The red mark on your diagram is a thermostat heater, makes the thermostat cycle faster for lower/delicate heats, the operating thermostat controls the normal on and off for the heat.

That is for heat only.

If the thermal fuse opens it should stay open, unless someone has changed it at one time?!!?

*Might* be able to carefully remove the timers cover to inspect the contacts and lifter cams inside.

jeff. Appliance Repair Aid http://www.applianceaid.com /
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Would you agree that if any of those were the problem, then it should show the problem on just about any cycle?

Opps, thanks for the correction. Is this thermostat located near the exhaust?

Good, so my problem can't be that.

Sounds like a good weekend project.
Thanks for the help Jeff.
Daniel
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Daniel S. Schudel
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Hi,

Normally yes.

Usually on the fan blower housing itself yes.

Please let us know what you find/see :)
jeff. Appliance Repair Aid http://www.applianceaid.com /
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I agree. It would also normally happen an all cycles as well, not just one.

Those would also usually effect all cycles as well.

I don't see anything else in the circuit besides the timer which is different between the auto and regular cycles and which could cause the whole dryer to shut down. I don't see an inspection plate on the timer used on that model (see the following link) so disassembly to view the contact might be tricky. But if it's going to be replaced anyway...
Kenmore 110.66702690 timer http://ng.appliance411.com/data.php?rcR8909

As soon as the dryer motor stops the start would need to be pushed to start it up again. A bad timer contact which heated due to not making firm contact might have enough time to cool and reset in the period between.
It would be unusual for such a bad contact to only fail once than operate Ok afterward but anything's possible in appliance repair. Maybe the timer's cam is damaged at one point? Did you notice if the dryer failed at exactly the same point every time or whether it was at even slightly different spots?
Dan O. - Appliance411.com http://ng.Appliance411.com/?ref411=Kenmore+dryer
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I've noticed the failure in more than one spot. I'm somewhat resigned to believing the problem to be somewhere in the switch. It's the one component in the circuitry that I *can't* eliminate.

an alternate like to your site that I can follow?
Thanks for the help, Daniel
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Daniel S. Schudel
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My site's been doing that lately unfortunately but seems to be working Ok now. But if you have problems you can try this one too:
http://www.repairclinic.com/referral.asp?R=4&NR8909
Dan O. - Appliance411.com http://ng.Appliance411.com/?ref411=Kenmore+dryer
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