How to Repair a Furnace Control Board

How To Repair a Gas Furnace Control Board

Furnace control boards (also called thermostat controls) are found in heating systems to measure and activate heat settings. The control board is typically mounted on the wall in a central location, but may be mounted in different locations in your home. Most are easy to read and understand, but there are some types of control boards that have additional features. Here are some of the more common problems when it comes to furnace control board repairs.


Turn the heat source down to check if this step actually fixes the issue. If the flame still doesn’t go out after activating the heat source, you should confirm that the safety switch and circuit breaker have been tested and are functioning correctly. A dry gas furnace blower that doesn’t turn off can also indicate a safety issue with a defective limit switch. (which might also need replacing or resetting).


In some cases, you will only need to check the limit switch. The flame sensor usually doesn’t require any type of maintenance or cleaning, but you should check it periodically to make sure it is not damaged or broken. A burned-out sensor is a serious issue that requires a furnace technician’s attention. It means there is damage to the flame sensor housing and may cause your furnace to cut power to the furnace for safety reasons.


Before performing furnace repair, always disconnect the flame sensor from the gas line. This is very important! Without this step, the flame sensor will continue to read as hot even if the gas is burned. If the furnace blows the gas onto the floor, it will ignite the flue gases and cause an explosion in your home. The explosion will blow out the ceiling and windows and can severely damage your home.


The next step is to turn the safety switch off. This step is also imperative. If you do not turn the safety switch off, you have a possible risk of the furnace exploding during startup or when starting the furnace. Without turning the safety switch off, it is possible for the furnace to burn itself out and cause an explosion or fire in your home. Turning off the safety switch also ensures that no one will touch the furnace during startup.


After you have disconnected the flame sensor from the gas furnace and turned the safety switch off, you should remove the restrictor and set the thermostat controls to the appropriate settings. You should also remove the gas furnace pilot light. Remove the screws and disconnect the limit switch, the electrical connection to the limit switch, and the wiring connections to the limit switch and the pilot light. You should now disconnect the furnace pilot light as well.


Step 2: Connect the Sensor to Its Own Circuitry – In this second step, you should connect the electrical sensor to its own circuit. In step 1, you connected the two wires to the heater sensor. There are three wires connected to the heating element. You should make sure that the corresponding wires are properly wired. If not, you should use a wire cutter or a good pair of wire cutters to cut the wires.


Step 3: Replace the Sensor in the Control Board – In the third step, you should replace the heating element to the appropriate connection. Then, you may need to test the connection between the gas furnace and the control board. If either of the wires fails to work, there may be a short or resistance in the wire. You should check the other three wires, as well. If the failure continues after you have tested the other three wires, you may need to have your gas furnace repaired.

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