Here are your parts
Replacement parts for Maytag NED7200TW10 29" ELECTRIC DRYER | AppliancePartsPros.comSee the attachment for the tech sheet, just in case you do not have it.
[COLOR="Blue"] I am torn now whether to continue to troubleshoot or just try it and hope I fixed it.[/COLOR]
I would just try it as a dirty vent system is the most common cause of this cut-off blowing. Also check that the outside vents open fully.
[COLOR="Blue"]The root cause could be that the heater never turns off.[/COLOR]
Not sure why you mention this.
Have you seen the dryer do this and if yes under what circumstances?
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Is TH3 (thermostat cut off in heater circuit) a temperature cycling device?[/COLOR]
No, it is also a thermal fuse like TH1
[COLOR="Blue"]Would TH2 thermostat (Hi-Limit) open before TH1 (motor ciricuit) would open?[/COLOR]
Not necessarily. They are protecting different areas in the air flow path.
So TH1 usually blows when there is a problem with the venting.
TH2 is limiting the overheating of the heater. So if you have a thermal run away due to a blown control board, a bad thermistor, a grounded element etc., it opens and cycles. What you would see is that the exhaust/drum temperature stays the same no matter what temperature you select (always runs on high). It is a safety device so is not designed to run a lot and eventually it's contacts will fail (can weld together). TH3 then blows as it is the backup for the hi-limit.
[COLOR="Blue"]What does the thermistor do in this dryer? Does it control the heater relay which could also cycle the heater?[/COLOR]
Yes, it's resistance changes with temperature. The control board reads the thermistor resistance and then uses that info to turn the heater relay on/off to regulate the temperature. This is the temperature control system.
The thermostats are all safety devices and should not open unless there is a prob;lem with the unit.
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The resistance of the heating coil itself was about 9.5 ohms. [/COLOR]
This is good.
[COLOR="Blue"]So, that reading probably does not tell us much other than it is not open.[/COLOR]
I could not find out if the thermistor is a PTC or a NTC. One increases resistance as the temperature rises. The other decreases the resistance with temperature increase.