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Kennmore66814

03:39AM | 08/23/08
Member Since: 08/22/08
4 lifetime posts
Bvelectrical
I have a Kenmore dryer (110.66814694) that shuts off part way through a drying cycle and it appears that it is from overheating. When it shuts off, the top of the dryer is warmer than normal to the touch and after it sits for a while you can start it again.

So far I have ruled out restricted air flow. The dryer vents outside near a door that is used frequently so I am familiar with what the normal airflow is and it seems to be normal. I have also checked for blockages and found none.

The motor starts and turns the drum normally. I have confirmed that by depressing the door safety switch manually with the door open and starting the dryer and it does turn normally. In addition, even with a full load if you select air dry with no heat it runs to completion and sounds normal.

That seems to me to indicate that it is thermostat problem. There are three thermostatic devices in this unit. There is a thermo cut-off (3399848), a thermostat 250F (3399693), and a thermostat internal bias (3387134). I believe that latter one is the problem and that it has failed closed. My reasoning is that if it was the thermo cut-off that turned the dryer off, it would not reset when it cooled. That leaves the other two and since it shuts off a higher than normal temperature it would seem the higher 250 degree thermostat is shutting the whole dryer off because the lower temperature internal bias thermostat did not turn off the heat.

Unfortunately there was no circuit schematic included with the dryer paperwork nor can I find one on-line so I have no idea if that is even the way the 250 degree thermostat works. Perhaps it only turns off the heater instead of the complete dryer which shoots my theory all to pieces.

I have not checked the continuity of the thermostats because since it is over heating, it would appear to indicate that they are all closed at room temperature, as I suspect they should be. I suppose I could take the internal bias thermostat off the dryer, attach a VOM to it with clip leads, stick in a baggy, and then put it into boiling water and see if it opens.

My thoughts at the moment however are that if someone here could advise me how the 250 degree thermostat works in the circuit, and if my reasoning is sound (big if), it would be reasonable to order the thermostat and have it on hand so I only had to pull the dryer out once.

DanO

09:11AM | 08/23/08
Member Since: 11/11/02
2271 lifetime posts
** Kenmore [electric] dryer [model] 110.66814694 **

That is a Whirlpool built model.

** shuts off part way through a drying cycle... after it sits for a while you can start it again. **

That is a common way dryer motors fail, their internal overload protector opening up when the motor overheats. That protector will normally reset once the motor has had a chance to cool again... until it fails totally.

Such a symptom is most often caused a problem in the motor itself but can also be caused by the motor just being plugged with dust and lint, etc. blocking its air vents. Basically, if the dryer's motor is getting power it should be running. Getting power but NOT running = defective motor.

- Kenmore 110.66814694 Dryer Motor

LINK > www.appliance411.com/data.php?ap=AP3094245

** When it shuts off, the top of the dryer is warmer than normal to the touch **

That can be caused by poor air flow through the dryer. A plugged, partially plugged or poorly installed (see the following link) dryer vent are the most common causes. A problem with the blower fan or the seals of the dryer drum could also hamper proper air flow through the dryer.

- How long can my dryer vent be?

LINK > www.appliance411.com/links/jump.cgi?ID=778

** The dryer vents outside near a door that is used frequently so I am familiar with what the normal airflow is **

That is antidotal evidence at best. I wouldn't rely on it as actual test results.

** I have also checked for blockages and found none. **

You've *thoroughly* checked for blockages in the dryer venting *all the way from the dryer to the outdoors* ??

** That seems to me to indicate that it is thermostat problem. **

Dryer thermostats usually shut the heater down, not the motor. Some models may have a non-resettable 'thermal fuse' which would open if the dryer got too hot.

** Unfortunately there was no circuit schematic included with the dryer paperwork **

No, it wouldn't normally be. There should however have been one on or in the dryer when it left the factory. On older models it could be pasted to the back of the dryer. On newer models it will often be inside the control console or inside the dryer cabinet.

JMO

Dan O.

www.Appliance411.com/parts/?ref411=Kenmore+Dryer

The Appliance Information Site

=D~~~~~~

Kennmore66814

10:51AM | 08/23/08
Member Since: 08/22/08
4 lifetime posts
OK. I will open it up and see what I find. I will report back one way or the other. Thanks for taking the time to reply.

Kennmore66814

04:49AM | 08/25/08
Member Since: 08/22/08
4 lifetime posts
I lifted the top and removed the front of the dryer. I also removed the drum to have a good view of the motor. There was some dust on it, but I would not have thought it was enough to restrict the airflow substantially. I did however vacuum all the dust out that was around.

I also completely disassembled the vent pipe system so I could examine it in its entirety. There was some restriction the full length much like an artery with heart disease but again it did not seem plugged. Since it was apart I did clean it completely so that it is now 100% clear the full length.

After reassembling the vent system and dryer we dried a load of clothes. After the first five to ten minutes during which it was running fine we left the area. Twenty or so minutes later when my wife checked on it, it had stopped much like before. I then positioned a chair next to the dryer with something to read determined to catch it in the act to see if I could immediately restart it after it stopped or if there had to be a cool down period first which might be the case if a thermal breaker had to reset. This time however, like a watched pot that never boils, it ran to completion (35 minutes) without a problem.

While I had the top up, I did note the schematic in the area behind the controls through an opening in the cover and retrieved it. After studying the schematic it is obvious that the three thermostats are in series with the heating element across both 120V legs (240V) and that there is no way a thermostat could affect the rest of circuit, including the motor, which operates on 120V between one leg and the neutral. I also noted however that the schematic shows only one non resetting thermal fuse in series with the motor. If there is an automatically resetting thermal breaker internal to the motor itself, it is not shown.

Unfortunately we are out of laundry at the moment and since there are just the two of us, it will probably be about a week before there is a need to use it again. I will however post the results when I do use it so others might benefit from my experience. The good news is that the vent is now definitely free flowing, and the internal areas of the dryer are cleaner than they have been in a long time. I also found several dollars in loose change under the drum so I made something for my effort ;-).

As an aside, the first link in your reply apparently redirects you to the site,

click.linksynergy.com. Firefox does not like that and refuses to connect. After doing some research on linksynergy.com, it is probably just as well.

DanO

09:52AM | 08/25/08
Member Since: 11/11/02
2271 lifetime posts
** I did clean it completely so that it is now 100% clear the full length. **

Good. That should be done seasonally.

** If there is an automatically resetting thermal breaker internal to the motor itself, it is not shown. **

There is and it might not be shown as it is not separately replaceable from the motor.

** Firefox does not like that and refuses to connect. **

I don't know why it wouldn't, it is a legit vendor marketing service.

** After doing some research on linksynergy.com, it is probably just as well. **

They just link to various vendors but you can try this vendor's direct link if you want.

- Kenmore 110.66814694 Dryer Motor

LINK > www.repairclinic.com/referral.asp?R=4&N=2584

JFYI

Dan O.

www.Appliance411.com/parts/?ref411=Kenmore+Dryer

The Appliance Information Site

=D~~~~~~

Kennmore66814

10:54PM | 09/25/08
Member Since: 08/22/08
4 lifetime posts
The first time I ran the dryer after the complete cleaning, it kicked out once as before and I thought I was looking at a new motor. Since we still had another load in the washer, I ran it again fully expecting I would have to restart it at least once to complete the drying cycle. This time it ran to completion and I did not have to restart it. We have since done perhaps a dozen loads and the problem has not resurfaced. I am at a loss as to why it kicked off right after the cleaning and has not done so since but I am not complaining. It looks like the thorough cleaning of the vent pipe and removing the accumulated dust around the motor did the trick. Thanks for your help.

BV000462

08:55AM | 02/27/13
My dryer seems to be ding many of the same things, but we also smell and "electrical burning". We think it may be the motor. Any way to troubleshoot and determine if that is the problem?

BV001088

03:54PM | 05/20/13
Consider the length of the exhaust duct. The ideal situation is for the dryer to be next to an exterior wall, with the hot air coming from the back of the dryer directly to the wall vent, or at most through 2-4 feet of flexible duct. If the duct is longer than 25 feet, or if there are several bends in a duct as short as 10 or 15 feet, there may be enough back pressure that airflow is restricted, causing the dryer to gradually overheat. Some sources say that airflow through a household dryer should be at least 100 cubic feet per minute (CFM). The solution in such a case is to install an inline dryer booster fan that starts automatically when the dryer comes on.

BV002494

03:59AM | 11/06/13
To BV000462, I had the same problem; dryer stopping and the smell of burning and even smoke in the drum. Turns out it was indeed due to the drive motor overheating and stopping, while the heating elements kept on going until their safety thermal cutoff kicked in, hence the burnt smell. After a few cooling down minutes, the drive motor was working again, but no heat in the tumbler. Since my dryer has a non self-resetting thermo-switch for the heating elements, I had to disassemble and reset the thermo switch manually with a little pin in the tiny center hole in the back of one of the "dime size" thermostats to get it heating again (gently pressing in until you hear and feel a little "click"). I am still working my way through the overheating motor problem though...
Hope this helps.
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