6 Furnace Troubleshooting Tips to Try Before Calling the ProsYour furnace system relies on a combination of equipment, ductwork and filtration equipment that must work together to deliver heated air to your living spaces. When one component fails, the entire system can shut down. With Indianapolis temperatures in the 50s or below for seven months of the year, that can be an emergency. If you’re able to discover that single malfunctioning element, you may be able to diagnose and even fix the problem yourself. If you have a conventional gas furnace, there are six relatively simple furnace troubleshooting tips you can try before calling the pros.


Check that your thermostat settings haven’t been inadvertently changed. The furnace won’t fire up if the control is not at “Heat,” or if the set temperature is below ambient room temperature.

Power Supply

Ensure the furnace has electricity. Even though it’s a gas-fired appliance, your furnace must have electricity to run. A tripped breaker or burned-out fuse may be the culprit, but this often indicates a failed component somewhere in the system.

Fuel Delivery

There should be a manual gas valve somewhere close to the furnace, on the supply line. Ensure that it hasn’t been kicked or knocked to the “Off” position (perpendicular to the pipe). If you’re on mains-supplied natural gas, find out if the utility provider has turned off the supply to carry out maintenance. If you use propane, ensure your tank isn’t empty.

Pilot Light

Older furnaces need a constantly-lit ignition source for their burners, the pilot light. It can be extinguished by a gust of air, or by debris failing into its jet. The flame must also be playing directly over the tip of the thermocouple.

Air Mover

Does the blower (fan) run? If it doesn’t, the furnace will not light. The capacitors that operate the motor, or the motor itself, may have failed.


A blocked air filter can close down your entire system. Check that yours has been changed recently, and replace it if it appears to be clogged.

If these furnace troubleshooting tips and remedies don’t do the job, you’re assured of prompt and professional service from Mowery Heating, Cooling and Plumbing. Call us today.

Our goal is to help educate our customers in Brownsburg, Indiana and surrounding areas about energy and home comfort issues (specific to HVAC systems). 

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