Furnace tries to start then shuts down

Furnace tries to start then shuts down. Is it sound familiar to you? Sometimes your furnace turns on, and right after a few minutes, it shuts down automatically, and then once again, it turns on, and the process continues. There are a few typical reasons behind this that are listed below: 

  • The heat exchanger is overheating due to low airflow
  • The dirty flame sensor rod
  • Oversized furnace

Furnace tries to start then shuts down
why furnace tries to start then shuts down

Read this article and find the easy solutions to fix your furnace instantly.

1. Flame Sensor

The flame sensor monitors the burner and detects whether the flame is present or not if the flame sensor cannot detect the flame control board.

It will automatically shut down the voltage of the gas valve to protect the furnace from overheating.flame sensor fault

And in case the flame sensor is defective and not working correctly, then it might be unable to detect the flame.

Sometimes flame sensor is also unable to work properly as it is all covered with dirt, would and in this case, it also becomes unable to detect the flame.

Try to clean your furnace regularly to keep your furnace safe. After taking proper care and following all the instructions, if your furnace is still not heating up, you should change the flame sensor. Read to Bypass flame sensor on furnace.

2. Control Boardcontrol board

The control board has the responsibility to supply power to every furnace component.

Your furnace can stop working if the control board is defective, and in this case, it won’t be able to send voltage to the ignition system, which will cause the furnace to shut off every few minutes.

And for this purpose, you need:

Furnace Control Board

  • Enter the model number to find out the required product for your furnace.
  • Browse the categories, read out the reviews before selecting any product, and make your purchase.

3. Draft Inducer Motordraft inducer motor fault

Draft inducer works to supply air into the heat exchanger and then through the flue air exhausts out.

Meanwhile, the pressure switch is responsible for sensing the pressure change and turning off the switch to send the signals t the control board that the furnace has enough airflow.  

 If the draft inducer motor is damaged, it might be unable to close to the pressure switch, and it will cause the furnace to shut down after every few minutes.

So if the draft inducer motor is defective, you can replace it as soon as possible.

Common Solution

4. Pressure Switchpressure switch fault

The pressure switch will turn off when the furnace has enough airflow. So if the pressure switch is defective, it might not be closed when the airflow is present, causing the furnace to shut down alternatively.

To test out the continuity of the switch, you can use a device called a multimeter, and if the pressure switch is not working with continuity, you can replace it.

Common Solution

5. Flame Rollout Limit Switchflame rollout limit switch

The flame rollouts work to monitor the heating level in the surroundings of the burners.

If the furnace is not venting, the inducer motor switch is not working correctly, and they cannot draw the air, the rollout switches will be opened and protect the furnace from overheating.

Multimeters can also be used in this case to find out whether the rollout switches are defective or not. Once you find out that switches have lost their continuity, you should replace them.

Also, ensure that your furnace has a proper and well-structured ventilation system, as they play an important role in keeping furnace performance intact.

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