Dryer Fixed and Adjustable Thermostats

Fixed Thermostats: Most fixed thermostats on Maytag, Kenmore, GE, and Whirlpool Dryers are composed of a bimetallic disc that snaps from a normal position to an opposite position when sufficiently heated. This bimetallic disc operates an internal switch in the thermostat which, in its normal closed position, is wired in series with the heating circuit. This switch may be single-pole single-throw, single-pole double-throw, normally open, or normally closed, depending on the circuit application Dryer Repair Los Angeles.

When a fixed-type thermostat is used as a high-limit or safety device, its purpose is to break the circuit to the heat source should the adjustable or fixed operating thermostats fail. If also functions in the event that some other mechanical failure causes abnormal temperature rises not detected by the operating thermostat.

Adjustable Thermostats: The physical make-up of most modern adjustable dryer thermostats is the same as the fixed thermostat but with one modification – a separate miniature heater element is piggy-backed on to the thermostat’s body.

When a controlled voltage is applied to the miniature heater element during the heat cycle, it causes a temperature rise inside the thermostat. The thermostat will now require less heat-rise from the heated exhaust air to reach its designed set-point. Once set-point or trigger-point is reached it switch will open and shut off circuit to the heat source.

When the air in the dryer cools the pressure inside the thermostat is relieved. The pressure release allows the internal wafer to return to its normal position, and the electrical current to the heat source is again active. The adjustable thermostat continues to cycle on and off during the entire drying operation, thus maintaining a stable drying temperature.

To troubleshoot an adjustable thermostat, insert a heat sensor (meter) into the exhaust outlet on the back of the dryer. Remove all clothes from dryer, turn on power, and monitor the temperature. The adjustable thermostat should open the circuit to the heat source at not more than 10F above or below the set temperature given for the part in the service manual. Let the adjustable thermostat cycle on and off five or six times to be sure you have accurate readings. First be sure there is not drum-seal air leak at the rear seal or the front opening.

If the component does not operate within the temperature tolerances as shown in the dryer service manual, replace it. Most any adjustable thermostats used on dryers cannot be repaired or adjusted.

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