Troubleshooting a Gas Furnace


In this article we are going to discuss common troubleshooting items that may help you diagnose your furnace. As each make and model of furnace is a little different, please treat this article as as guide but not a manual. A furnace can malfunction as a result of many different things. As multiple components work together in order for a furnace to operate properly, all it takes is one small part of the larger whole failing for the entire furnace to be rendered inoperable. If you’re having problems with your furnace, try the items below before giving us a call.

External Equipment – Thermostat & Ducting

Thermostat Problems

One common reason a furnace fails to operate properly is because the thermostat itself is malfunctioning. Remember, the furnace gets its instructions from the thermostat. If the thermostat is malfunctioning, it may appear that the furnace is the problem when in reality it may be simply following incorrect instructions. Check that your thermostat is operating correctly and that it is sending a signal to the furnace. Your owners manual will have specific troubleshooting steps to help you determine if this if it is operating properly or not. Generally, when setting the temperature, you will hear a mechanical click when the thermostat engages the furnace. This may not be true of all thermostat makes and models.

Blocked/Leaky Ducting

If your ducting leaks a lot, or is blocked, your furnace may be unable to keep your home comfortable and at an even temperature. If the furnace turns on and engages, but the home doesn’t seem to heat, check to see if there’s airflow coming from the vents. Sealing and insulating your home’s ducts can improve your heating system’s efficiency by up to 20%.

Airflow – Filters & Fans

Furnace Filters

The furnace filter is placed at a choke point between your furnace and your home’s cold air intake. It’s purpose is to ensure the air flowing through the furnace is clean of debris and particulates. This keeps your furnace clean and also filters the air at the same time. If your furnace filter is really dirty and clogged, it will have a noticeable impact on airflow. Replacing an old filter can improve furnace efficiency immensely. Furnace filters should be replaced whenever they are dirty, or every three months- whichever is sooner.

Furnace Fan/Blower Motor

If you can hear your furnace burners engage but the furnace fan does not turn on to blow warm air throughout your home, chances are that your blower motor/furnace fan may require servicing or replacement. You can test this by turning on your home’s ventilation fan via the thermostat. If the fan engages fine that way but does not engage in conjunction with the furnace, call us for a estimate for a furnace service.

Heat – Burners, Pilot Lights, & Heat Exchangers

Gas Burners

When a gas furnace engages it sounds similar to how a gas/propane barbeque sounds when it is first ignited. If the burner nozzles are clogged, or if the ignition system fails to ignite the gas, your furnace will not be able to produce heat.

Pilot Lights

If your pilot light will not remain lit, follow the instructions in the owner’s manual to attempt to relight it. If it doesn’t light, call us for a service.

Cracked or Damaged Heat Exchangers

If your furnace and blower motor both properly engage, yet warm air still does not circulate throughout your home, your heat exchanger may be to blame. If the heat exchanger is cracked or damaged, it will be far less effective at heating the air.
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866-792-7154