5 Reasons a Furnace Starts Then Stops
No one wants to have furnace problems during winter. Dealing with a furnace that starts then stops is a peculiar problem for most homeowners. Discover what's the source of the issue with this helpful guide. We've listed the parts associated with solving a furnace that starts then stops below.
Malfunctioning Flame Sensor
The flame sensor monitors the burner to detect whether or not a flame is present. A malfunctioning flame sensor may fail to detect the flame, causing the control board to shut-off voltage to the gas valve which will stop the furnace from heating. If the flame sensor is dirty, you can try to clean it with a fine abrasive pad. If the flame sensor still doesn't work, you will need to replace it with a new one.
Faulty Pressure Switch
Adequate airflow through the draft inducer motor housing will cause the pressure switch to close allowing the ignition process to continue. A faulty pressure switch may be unable to close, stalling the ignition process and shutting-off the furnace. You can use a multimeter to determine if there is a continuous electrical path present in the switch, provided the switch is connected to the furnace and the draft inducer motor is running. If there is no electrical continuity, then the pressure switch has failed and will need to be replaced.
Defective Control Board
The control board regulates the power supply to all of the furnace components. A defective control board may not send voltage to the ignition system, causing the furnace to shut-off after a few minutes. Then, the control board is defective and will need to be replaced.
Faulty Draft Inducer Motor
The draft inducer motor draws air into the heat exchanger, then exhausts it out of the flue. Since proper airflow is required for the pressure switch to close, and the ignition process to begin, a faulty draft inducer motor unable to maintain the airflow can stall the ignition process and shut-off the furnace after a few minutes. Then, the draft inducer motor is faulty and will need to be replaced.
Air Flow Problem
In order to continue running, the furnace requires sufficient airflow through the burner. Poor airflow is often the result of insufficient ventilation or restricted inlet or exhaust vent. Make sure your furnace is in a properly ventilated location and the vents are clear of obstructions.
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Commonly replaced furnace parts: