Troubleshooting Furnaces: 8 Furnace Repair Parts You Might Need to Buy

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Last updated: 
April 7, 2024

Why is my furnace not heating the house?

There can be several reasons why your furnace is not heating your home. According to our research, we've collected the most common issues below, but be advised that testing some of these hypotheses will require the aid of a qualified professional, plus the purchase of furnace repair parts. The parts that might be causing you trouble have been listed in order of how commonly they occur, starting with the most troublesome ones.

Common furnace issues


The igniter that's supposed to light up the gas flame may not be working properly. All furnace igniters have 120 volts running through them, provided by the main control board of the heating unit. When functioning correctly, it should glow a bright orange. A cracked or faulty igniter will need to be replaced.

Flame sensor

The flame sensor, which monitors the gas burner, may be failing to properly detect the flame. This can cause the control board to stop supplying power to the gas valve, halting ignition. Try cleaning the flame sensor with an abrasive material (nothing too harsh) before considering a replacement. If the problem persists, a new flame sensor will be necessary.

Draft induction motor

A malfunctioning draft induction motor can prevent the furnace from properly drawing air into the burner unit. Normally, this air would flow through the furnace and out the flue. A pressure switch inside the burner unit must be closed by this airflow to indicate proper operation to the main control board. Without activating the switch, ignition may fail to start or be delayed.

Main furnace control board

Many issues requiring furnace repair parts and professional assistance stem from improper ignition. If the furnace's control board is at fault, a replacement will be necessary, as repairs are very complicated. A malfunctioning control board may fail to provide the required voltage to other ignition components.

Flame rollout switch

The flame rollout switch regulates heat around the burners. Normally, burner flames should be directed into the heat exchanger and exhausted through the flue. A malfunctioning roll-out switch may fail to acknowledge this process, open, and stop the furnace's heating. This is often caused by insufficient air in the furnace room or a blocked exhaust vent. Before purchasing furnace repair parts, check that vents and registers are not obstructed by rugs, furniture, or other items.


Ensure all contacts inside your wall thermostat are functioning properly. If they're not, your furnace will be unable to heat your house as desired.

Gas valve

During ignition, the furnace's main control board sends 24 volts to the gas valve assembly. A malfunctioning valve may not open properly, preventing gas from flowing to the burners. First, ensure the issue doesn't lie with the control board. If proper power is flowing through the valve, but it still fails to open, the valve is likely the culprit.

Pressure switch

During draft induction, air flows through the furnace burner, and a pressure switch is flipped at the end of this process, indicating proper airflow to the main control board. If the pressure switch doesn't close, ignition cannot occur.

Troubleshooting situations unrelated to furnace repair parts

In addition to the scenarios above, ensure your furnace is properly supplied with all it needs to function correctly. Here are some common supply-related situations that could cause your furnace to malfunction:

  • Insufficient gas supply: Ensure the gas valve is turned on. If it is, your gas company may be at fault. If your furnace runs on propane, check the fuel levels.
  • Insufficient air supply: Check the manufacturer's ventilation recommendations before installing a furnace. Some units may "choke up" due to a lack of sufficient air when mounted in a closet or other small, poorly ventilated space. If your furnace draws air from outdoors, ensure the inlet is not blocked by any foreign object.
  • Insufficient power supply: Check the circuit breaker or fuse for your furnace in the appropriate fuse control panel if it seems like the furnace isn't getting enough electricity.

By addressing these common issues and ensuring proper supply, you can troubleshoot and resolve many furnace problems that prevent your home from being properly heated.


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