Thermal Cutoff Issues

Dryer Repair
1

Greetings all,

The thermal cutoff on my Kenmore dryer went bad about a month ago. I checked continuity on all of the temperature control parts and had good continuity on all of them except the thermal cutoff. I ordered a new part, and it came with the high limit thermostat as well. Since the only problem was the thermal cutoff I replaced it, but not the high limit thermostat. Two days later I again had no heat, and again had no continuity across the thermal cutoff. I tore the dryer apart looking for blocked air flow, and found everything to be clear.

So my question is this. Is it possible that the high limit thermostat is stuck closed, and that is what is causing the thermal cutoff to go bad? I know I’m an idiot for not replacing the high limit thermostat…I should have known that if they are sent as a set to replace them both, but hey, sometimes I’m an idiot!!!

Thanks

Dave Thomas
Terre Haute, Indiana USA
dthomas@davidandellie.com

2

Here is your parts breakdown.
Replacement parts for KENMORE 11096592400 | AppliancePartsPros.com

I think “idiot” is a bit strong, you just made a minor mistake.
In any case the hi-limit is not your problem.

I am assuming that the fuse is the one on/close to the heater.

Since it is blown you have to find out what caused it to go.
Note: that sometimes they do just blow on their own but changing it without checking other things is a gamble. You gambled and lost.

Check the heating coil.
Unplug the unit and both wires to the coil.
Check it with a meter, should be around 10 to 12 ohms.
Then check from each side of the coil to the case/frame, both should be infinite ohms (open). If not the coil may have sagged or broken and is touching the case. This can cause it to run on high and the thermostats cannot regulate it so the thermal fuse blows.

If the above is OK then you will also have to replace the hi-limit as it should have regulated the temperature so the fuse did not blow.
Note: That unless there is another problem in the unit the hi-limit should never have to open. It is just a safety device with the fuse being a backup safety device.

You still have to find out why it blew.
Check that the belt is OK.
Check the seals (drum etc) in the unit. The air is pulled over the heating coils, through the drum and pushed out the exhaust. So any large seal leak will pull in room air and the cycling thermostat on the blower will run the unit hot.
Check that the lint filter is not coated with fabric softener residue which greatly reduces air flow.
Check/clean your vent system.
Check/clean the blower wheel.

If all OK you may want to replace the cycling thermostat as it’s contacts may not be opening (welded shut).

3

Thanks for the response…

The element is brand new…when our dryer initially stopped heating we suspected the element and replaced it. The new element looks good with no sagging or any other issues.

I did tear the dryer apart and found no airflow problems. The drum seals were good, and the blower wheel and lint system are clear. The element shows values as you suggested. The thermal fuse shows continuity as well.

I ordered a new thermal cutoff/high limit thermostat set. I’ll replace them both this time, and if the TCO goes bad again I guess I’ll have to break down and take it in for service. When I had it torn apart I saw nothing blocked, and everything showed continuity except the thermal cutoff…but that is what keeps going bad, so the problem has to be elsewhere…very unlikely that I received a bad thermal cut off…but possible I suppose.

Thanks again. I’ll post again if I have any more questions.

[QUOTE=denman;314773]Here is your parts breakdown.
Replacement parts for KENMORE 11096592400 | AppliancePartsPros.com

I think “idiot” is a bit strong, you just made a minor mistake.
In any case the hi-limit is not your problem.

I am assuming that the fuse is the one on/close to the heater.

Since it is blown you have to find out what caused it to go.
Note: that sometimes they do just blow on their own but changing it without checking other things is a gamble. You gambled and lost.

Check the heating coil.
Unplug the unit and both wires to the coil.
Check it with a meter, should be around 10 to 12 ohms.
Then check from each side of the coil to the case/frame, both should be infinite ohms (open). If not the coil may have sagged or broken and is touching the case. This can cause it to run on high and the thermostats cannot regulate it so the thermal fuse blows.

If the above is OK then you will also have to replace the hi-limit as it should have regulated the temperature so the fuse did not blow.
Note: That unless there is another problem in the unit the hi-limit should never have to open. It is just a safety device with the fuse being a backup safety device.

You still have to find out why it blew.
Check that the belt is OK.
Check the seals (drum etc) in the unit. The air is pulled over the heating coils, through the drum and pushed out the exhaust. So any large seal leak will pull in room air and the cycling thermostat on the blower will run the unit hot.
Check that the lint filter is not coated with fabric softener residue which greatly reduces air flow.
Check/clean your vent system.
Check/clean the blower wheel.

If all OK you may want to replace the cycling thermostat as it’s contacts may not be opening (welded shut).[/QUOTE]

4

Well if you notice that the unit is always running on hot then you know that the hi-limit is regulating the temperature and so the problem is still there.

If everything else looks good then the main thermostat could be the problem re: it’s contacts are welded together.

It is a 4 wire thermostat so take note which wires go where
2 for the contacts and 2 for an internal heater, that is turned on for lower temperature settings. This then cycles the thermostat more often.

You could remove it, place it on a stove element and see it the contacts open.
Just be careful you do not want to burn your fingers.

Not a definitive test but at least it is a test. It should open at 155 degrees.

5

[QUOTE=denman;314791]Well if you notice that the unit is always running on hot then you know that the hi-limit is regulating the temperature and so the problem is still there.

If everything else looks good then the main thermostat could be the problem re: it’s contacts are welded together.

It is a 4 wire thermostat so take note which wires go where
2 for the contacts and 2 for an internal heater, that is turned on for lower temperature settings. This then cycles the thermostat more often.

You could remove it, place it on a stove element and see it the contacts open.
Just be careful you do not want to burn your fingers.

Not a definitive test but at least it is a test. It should open at 155 degrees.[/QUOTE]
denman…

I received the new parts and put them on. While I was putting things back together I noticed that the bottom part of the cover over the blower fan dod not appear to be sealing correcly. Upon further investigation I saw that there was a clip that is supposed to go on the bottom of the cover. I had not replaced this clip last time I replaced the parts, and I wonder if this perhaps caused the airflow to not route properly, causing the thermal cutoff to again go bad. I replaced the clip properly, and the cover is now sealing over the blower fan assembly. Could this have been why the thermal cutoff went bad again after only two days?

Thanks for your help.

Dave

6

Yes it could if the high limit was also bad (contacts welded together)/
It may have sucked in room (cold) air so the main thermostat registered a colder temperature and ran the dryer hotter than it should have.