Temperature Controls And Hi-temp Safeties (Figure W-6)
These clothes dryer machines use operating thermostat so control the temperature inside the drum, and hi-limit stats to prevent overheating of the dryer drum.. Many machines also have extra temperature controls, such as bias thermostats and heaters, hi-temperature cutoffs, and thermal fuses.
Bias thermostats are just like regular operating thermostats, except that they are mounted inside a bias heater. When the bias heater is energized, it generates a small amount of heat, which causes the operating thermostat to open sooner, keeping the dryer drum cooler inside. Thus a bias heater allows a single operating thermostat to act like both a hi-temp and a lo-temp operating thermostat.
A thermal fuse is found on the blower outlet, right next to the operating thermostat(s.) This fuse will blow when too high a temperature is sensed at the outlet; usually when one of the operating thermostats has failed. If it blows, the motor may not start, or you may get no heat (no voltage to the burner.)
A thermal cut-off is mounted on the clothes dryer heater box. It is a back-up for the hi-limit stat. Whenever you replace it, you should replace the hi-limit stat, too. A high-temperature condition causes it to open, an overheated grounded heat element may also cause it to open.