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The problem my dryer expresses is that it is not heating. I had replaced the heating coil and the High limit thermostat a few months ago for the same symptoms. The heating coil in that case had a physical break. I know that the blower functions as I can feel air coming out when it is on with the exhaust disconnected.

I checked the coil and it has continuity from end to end and no continuity with the frame. So the heating coil looks okay this time. I also tested the high limit thermostat continuity and thermistor and those seem in spec as far as I can tell (continuity and 60k ohm).

I measured ohms on the internal-bias thermistor (or cycling themsister?) and it came back as 5-6 ohms at 70 degrees. This is about 1/2 of the suggested 10 ohm for in spec. This would potentially explain my issues. However, even on high heat the dryer seemed to have no heat.

My understanding is that lower resistance than spec on the cycling thermistor would make the dryer think it's hotter than it is, meaning it would not want to heat, but if this was the sole cause of the issue would I not expect to see a little heat on the hottest setting if there is some resistance? Is this a correct assessment?

The other part that is confusing that might explain some things is that the thermal cut off has no continuity. As I understand it this blows out when things are way too hot, but before this blows it is meant that the High Limit Thermostat would trigger first. i.e. it's a fail safe.

So here comes the punch line. How would the thermal cut off break continuity if the high limit thermostat seems fine, but is supposed to trip first? Is it possible it broke the first time I repaired it and then the replacement of the high limit thermostat allowed it to work again even with the thermal cutoff blown?

I can't figure out if my testing is wrong, my understanding is wrong, or what I'm missing. I'm going to probably replace all three parts here to be sure, but I'd like to understand the aspects at play here. I used a couple steam cycles prior to this recent break. I don't know if that is pertinent or not.

In Summary

First repair: I replaced the heating coil and High Limit Thermostat about three months ago. Dryer started heating again and worked fine.

Second Repair I am doing now: heating coil and high limit thermostat appear to be fine. I am investigating:

1 Answer 1

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Is it possible it broke the first time I repaired it and then the replacement of the high limit thermostat allowed it to work again even with the thermal cutoff blown?

Sure it's possible.

The incident that caused the heating coil to physically break may have also damaged (but not caused complete failure of) the thermal cut off. Whether it was an actual high-heat incident that caused them both to go, or possibly an electrical incident caused by the physical break that caused the cut off to fail, they may have happened at the same time.

Since it worked for a time after the first repair, there may have been partial damage at that time that has finally failed completely.

In either case, it seems like it's time to replace the thermal cut off, and you may as well order & replace the internal-bias thermistor since it doesn't seem to be functioning properly either.

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