How to check and solve common furnace problems?

How to check and solve common furnace problems?

- in Home Improvement

When it comes to gas furnaces or any other, there are many things that can go wrong. Sometimes it is hard to establish what the problem is, but in many cases, you can check and solve the problem yourself. Calling for professional help can cost much depending on the problem. It won’t cost you anything to see if you are able to fix it on your own.


If the furnace ignites and the blower fan is running, but there is no heat coming out of the registers, then something might be restricting the airflow. Turn off the furnace and check the filter. It is located next to the cold air return duct. As the filter collects dust, it begins to restrict the airflow. This is why it is essential to replace the filter every three to six months. If replacing the filter doesn’t help, there might be something else clogging the ducts.

Simple solutions

If your furnace isn’t running at all it is best to eliminate the simple solutions first. Check everything about your thermostat. Maybe batteries are the problem, so you should replace them to make sure. Read more about it here.

Check the breaker box to find if the furnace breaker is tripped and in the middle position. Then flip the breaker all the way off and then flit it on to reset the breaker. Locate the power switch on the side of the furnace and make sure that the switch is on. Next thing you should do is to find a gas valve. It should be open.

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Also, many furnaces have a safety switch that prevents the furnace from running when the blower cover is open. Make sure that the cover is closed all the way.

Safety switches

Modern furnaces have a set of safety switches that shut down the furnace when the system is compromised. If a switch is tripped it will cause the furnace to lock-out. The furnace will attempt ignition several times before going into a hard lock-out for up to an hour.

Every time a lock-out happens, the furnace will use flashing lights as codes to identify the source of the shutdown. These codes are unique to each model, so check your furnace manual to see what each code means. Don’t try to do everything by yourself. It is smart to let the professionals handle it.

Draft inducer

If your furnace has power, then turn on the thermostat and observe the startup sequence. First, the draft inducer fan pulls air through the heat exchanger. This ensures that all fumes are exhausted during combustion. If the inducer isn’t running then the motor might be seized or burnt out. Additionally, the wires could be faulty it could be a problem with the control board.

Pressure switch

If the inducer is running and there is enough airflow to remove the exhaust gasses, then the pressure switch will close. When the pressure is low, the switch will stay open, and prevent the furnace from igniting. Try to identify anything that might cause a change of pressure inside the heat exchanger. Check to see if there are any obstructions in the flue vent or in the inducer motor port. Also, check if there are any blockages in the pressure switch tubing. You can fix the pressure switch on your own, just read more about how to do it, to make sure nothing will go wrong.


If the pressure is good, then the voltage is sent to the hot surface igniter. Some furnaces might use a spark igniter instead. If the igniter doesn’t activate, then remove it and test for continuity. If it doesn’t have continuity, it will need to be replaced. If it has, the problem can occur at wires.

Gas valve

As the igniter glows, the gas valve will open and the burners will ignite. If there is no flame present, check to see if the gas valve is on. If there still is no flame, you should call a professional for help. They will check the solenoid gas valve for damages.

Flame sensor

The flame sensor indicates that the flame is present. If all the burners light, the flame should stay on for more than seven seconds. If the burners shut off shortly after igniting, the flame sensor could be dirty or defective. Remove the sensor and clean it, if the flame still doesn’t stay on, then replace the flame sensor.


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