How To Fix An Ignition Lockout On A Furnace?

A furnace plays an integral role in keeping you warm throughout the winter, which is why it is extremely important the problem is fixed and the furnace starts functioning as intended. 

What is an ignition lockout?

A furnace can be dangerous if not maintained well or if it interacts adversely with external elements. This is why all furnaces have certain safety measures to keep the unit in check and functioning as intended. One of these measures is the ignition lockout, which occurs when a sensor detects an unsafe condition or a malfunction. It forces the furnace to shut down to prevent damage and maintain safety.

What Can Cause A Furnace Ignition Lockout?

Here are a few reasons that can cause a furnace ignition lockout:

  • Limit Switch: A limit switch monitors the temperature and air pressure in the heat exchanger. If the temperature or the pressure is too low, the limit switch will alert the furnace to shut down and enter the ignition lockout mode. The pressure may also be low because of dirty filters, which may also cause the furnace to shut down.

  • Defective Flame Sensor: When a furnace is turned on, a flame sensor is used to detect the presence of a flame. If the sensor is dirty, blocked, or defective, it does not register the flame as turned on and makes the controller turn off the ignition process. This is one of the most common reasons for an ignition lockout.

  • Faulty Igniter: A furnace igniter is responsible for turning on the flame. Thus, if it is faulty or takes too much time to start the flame, the flame sensor will not be able to detect its presence and will turn off the ignition process, going into lockout.

How Do You Fix A Furnace On Ignition Lockout?

If your furnace is on ignition lockout, it might require a repair or replacement and heating installation in Cheltenham. It is advised to hire an HVAC professional, such as Heath Mechanical Services to help service and fix the heating.

However, here are some common troubleshooting methods you can employ for a quick fix:

  • Clean Or Replace The Air Filter: Frequently, the furnace’s pressure is too low due to a dirty and clogged air filter, which can lead to an ignition lockout. If this is the case, you must clean and unclog the filter or buy a new one, and the furnace should start working again.

  • Inspect The Vent Pipes: Sometimes, debris gets stuck in the pipes, preventing proper airflow, obstructing sensors, and not letting enough heat through. Cleaning and removing this debris will allow higher pressure and more accurate readings for things like the flame sensor.

  • Clean Or Replace The Flame Sensor: If it is faulty or broken, replacing it is the only option to ensure the furnace can register the flame and start functioning. If it is blocked by debris, cleaning the sensor should get the job done!


If your furnace is facing an ignition lockout, you might be searching for “What are good heating repair services near me?” online. Check out Heath Mechanical Services for HVAC servicing and heating installation in Cheltenham, and get the best services to solve all your problems!