Furnace Fan Temperature Sensor

A typical limit switch consists of a long temperature sensor probe attached to a mounting plate.

Furnace fan temperature sensor.

Once the flame sensor has been cleaned and reinstalled turn the power back on. Thermometrics manufactures thermocouples that meet furnace certifications as well as magnesium oxide mgo thermocouples that can be formed to fit almost any application. Lightly clean the surface with fine emery cloth and slip the sensor back into its bracket. The flame sensor occasionally becomes coated with residue and will prevent your furnace from lighting.

In the heat treating industry temperature sensors must be able to handle exposure to extreme temperatures and conditions. Honeywell l4064b2236 combination fan and limit furnace control. Things to check first. A blower fan manual on switch is also included on many fan limit controls.

Honeywell st9103a1002 u replacement electronic fan timer for oil furnaces 60 90 120 150 sec. The mounting plate usually contains two or more terminals that receive control wires for the blower fan and the furnace s gas valve. In the video you can see 4 burner ports. Remove it by pulling it down out of its bracket.

Once you have cleaned the flame sensor make sure no wires from the igniter or flame can get in direct contact with the flame. Upon removing this screw the sensor will slide out so that you can easily clean it. A high limit setting which turns off the heat source or burner if the furnace overheats to dangerous temperatures. Conclusion gas furnace number 1 problem flame sensor.

Be sure the filter is good. A clogged up furnace filter will block air flow into a furnace and raise the temperature inside it. Between the 1st and 2nd burner ports from left to right you can see the wire leading to the flame sensor the sensor is easily accessible and typically mounted by one 1 4 hex head screw. The gas furnace should fire and you will have heat once again.

A temperature sensor within the furnace. If the temperature inside the unit becomes to high the high limit switch will turn the gas off to the unit. A control which turns the blower fan on or off depending on the air temperature within the furnace.