Here are your parts
Replacement parts for WHIRLPOOL LE5720XSW0 Residential Dryer | AppliancePartsPros.comSee the attachment for a wiring diagram. I could not find a XSW0 so diagram is for a XSW1 which should be close it not the same.
[COLOR="DarkRed"] And why or how, if that is the case, would the therm. switch keep blowing?[/COLOR]
The cycling thermostat is on the blower assembly and you are blowing the thermal cutout on the heater assembly basically you are measuring the temperature in a different temperature zone so that can cause problems. As an example lets say room air is being sucked into the air flow path before the cycling thermostat, it sees a cooler temperature so turns off when the heater is hotter than it should be. Plus there are other possibilities.
[COLOR="DarkRed"]Why would it matter if there is a restriction in the venting system if the coils on the heating element are turning on and off with the t-stat?[/COLOR]
It all depends when they turn on/off. Also usually it is the thermal fuse that blows when there is a vent restriction.
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 cut-off blows.
In your case it could be that it has failed in such a way that the thermostat can control it but it is putting out too much heat on a short piece of the element and pooping the ther,mal cutout.
The hi-limit should have regulated the temperature so the fuse did not blow, that is why there is a new one with the thermal cut-off..
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.
Just in case it is not a grounded element.
With all the below the high limit will also have to be replaced.
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 at the correct temperature.