Replacement Hi-limit Cut off Thermostat & Resettable Thermal Switch

Hi-limit Cut off Thermostat & Resettable Thermal Switch When the circuit is working properly, the contacts are in a closed state. When the rated operating temperature is reached, the bimetal is deformed by heat and breaks quickly, cutting off the circuit. After that, the device begins to cool down. When it reaches the specified reset temperature, the bimetallic strip and spring strip snap back to their starting position, the contacts will close again, and the device will start working again.

Multi-mount Manual Reset High Temp Limit Safety Switch L350°f For heater

215° Resettable High Limit Thermostat

Ceramic Hi Limit OVER HEAT & Hi-Amp Thermal Cutoff Switch 240F

Replacement Resettable Thermal Cutoff Switch process:

Multi-mount Manual Reset High Temp Limit Safety Switch L350°f For heater.
The fuse on the heater is a safety device. The hi-limit thermostat should control the temperature so that the fuse does not blow. Therefore if the fuse does blow the hi-limit thermostat is not regulating the temperature so it is assumed that it is toast. Note that the hi-limit thermostat is also just a safety device.

If the unit is running on the hi-limit thermostat, this indicates a problem as the hi-limit thermostat should not be regulating heater temperature, the cycling thermostat on the blower should be doing this.

You may have a grounded element (the element has sagged or broken and is touching the case) in which case none of the Hi-limit Cut off thermostats can regulate the temperature. Often you can see this by inspecting the heater assembly.
It can be checked with a meter.
Unplug the unit and remove the wires from the heater. Measure the heater should be around 10 ohms. Then measure from each connector to the case/frame both should be infinite ohms (mở).

Another possibility is a restriction or leak in the air flow inside the unit.
The dryer is actually sucking air over the heating coils, through the drum and then pushing the air out the exhaust. If the lint filter is coated with fabric softener residue this can reduce the air flow significantly causing the heater to run hot.

Also the operating/cycling Hi-limit Cut off thermostat is on the blower wheel so if the unit is sucking in air through a blown seal, it sees a cooler temperature at the blower and again causes the heater to run hot.