Furnace maintenance should be done on a regular basis. The best time to do so is in late summer or early fall, when you still have enough time to address any problems before it gets too cold outside.

HVAC systems malfunctions are typically caused by one of a handful of common problems. Inspecting certain components can help to guarantee a furnace is in working order when the first cold days arrive.

Filter and air intakes

After several months of running the air conditioning, the filter on the heating and cooling system may need to be changed. Check the condition of the filter to see if it is heavily soiled. Furnace filters are relatively inexpensive. Since this thin barrier will be responsible for cleaning the air you breathe, it is important to keep a fresh filter in the unit.

A clogged, dirty filter will reduce the efficiency of the HVAC system and may contribute to poor indoor air and allergies. Check the air intakes around the house for obstructions.

Do not place furniture directly in front of intakes or venting that delivers air to the home, as this can compromise air flow and force the unit to work harder. Without adequate air flow through the system, the furnace may not turn on.


Many systems also have some sort of external vent or exhaust pipe. Check that the area is free of leaves, debris and animal nests. Again, any blockages can impede the efficiency of the unit or cause it to fail.


Very often a furnace may not turn over because the thermostat is faulty. Many a homeowner has spent money to have a service person come out to examine the furnace, only to learn they only need a new thermostat or battery in the thermostat.

Check the thermostat against a separate thermometer to ensure that it is reading the right temperature in the house. Raise the setting a few degrees to test if the heat kicks on.


Furnaces are powered by various energy sources. Electricity, gas or oil may be involved in the process. If fuel is not being delivered to the furnace, the pilot will not light and warm the air to be blown through the house.

Some systems have an emergency shut-off switch that will halt fuel delivery to the unit. It’s easy for these switches to be flipped accidentally if a furnace is located in a high-traffic area. Make sure the switch is in the “on” position before reporting a problem.

In addition to these steps, you may want to vacuum the vent screens around the house. This will reduce the amount of dust blown around. Also, if the furnace exhausts into a flue, be sure that the exhaust route is clear so that carbon monoxide does not back up into the home.

Many homeowners are fully capable of inspecting their furnaces to ensure they are ready for winter. If anything seems out of place or malfunctions, consult with an HVAC professional to make repairs. 

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