On furnaces, a fan limit switch uses a heat sensor to detect the temperature of the air passing through the valve that the switch is affixed to. Its purpose is to detect when the air in the furnace is warm enough to circulate into a home. Without the fan limit switch, the furnace would blow cold air.Know More
The fan limit switch in a furnace is also able to detect when the air temperature has fallen below a certain limit. When this occurs, the fan limit switch instructs the furnace to turn the blower off. The switch doubles as a safety measure that turns off the burner in the event that the furnace's heat temperature reaches a dangerous level.
Furnaces make a familiar noise for several minutes before they begin to release air. This is the time during which the furnace is heating the air to an acceptable temperature. The fan limit switch is responsible for withholding the air from circulation until the furnace has heated it sufficiently. If a furnace blower begins to run continuously without turning off, a homeowner needs to check to make sure the fan limit switch is in proper working condition. If not, the homeowner must call a professional to make the necessary repairs.Learn more about Heating & Cooling
To troubleshoot and reset a furnace limit switch, ensure the furnace is receiving power, turn off the furnace switch, replace the filter and test and replace the high-limit switch. Consult a professional with questions or to perform any necessary repairs.Full Answer >
To replace a speed switch on a Hunter fan, unscrew the fan switch chain guide to release the 4-wire speed switch. Pull the switch from its housing, note the labeling of the connections and disconnect the wires using a straightened paperclip. Connect the replacement switch, and test.Full Answer >
The high temperature limit on a thermostat prevents the temperature in the area being monitored from exceeding its set point. For example, household dryers have a high temperature limit thermostat, sometimes called a safety thermostat, that shuts off the heat when the temperature reaches 240 degrees.Full Answer >
Find the correct type of replacement for the defective limit switch. Turn off the furnace and remove the old limit switch by separating the connecting wires and unfastening the holding screws. Install the new switch, place the doors back on the furnace and turn the power back on.Full Answer >