If you notice that your gas furnace is not providing heat, chances are pretty good that you will need the assistance of an HVAC contractor, like Paitson Bros. However, there are some common troubleshooting guidelines you should follow prior to calling a professional service technician.

In this article, Paitson Bros. experts share our most helpful no-heat checklist so you can identify and resolve common problems with your non-functioning heating system.

Thermostat Check

If you want heat, make sure the temperature control selector is set at least 3 degrees above room temperature and the SYSTEM switch is at HEAT or AUTO. The FAN switch should be set at ON for continuous blower operation or AUTO if you want the blower to function only while the unit is operating. If the thermostat is set properly, the next step is to check to see that there is power to the furnace.

Electrical Check - Furnace

Check disconnect switches (indoor and outdoor if you have a split system). Make sure that circuit breakers are ON or that fuses have not blown. Is the furnace plugged in? Is the power to the furnace turned on?

Some heating systems also have emergency cut-out switches that are activated when a door or service panel is removed. Often the furnace door is not closed properly after a filter cleaning and the cut-out switch will prevent the furnace from coming on. Check to make sure all furnace access doors are properly secured.

Pilot Light and Ignitor

Is the gas turned on? If you have LP gas maybe your tank is low on gas and needs refilled.

If you don't have an automatic pilot lighter, is the pilot lit? Generally furnaces prior to 1986 do not have automatic pilot lighters.

If you have an automatic ignition system, the furnace may lock-out if it has a problem. On most furnaces you can unlock the ignition by turning off the power to the furnace or turning the thermostat to the off position for a few seconds and then back on again. You should call for a qualified service technician even if the furnace comes on so the source of the trouble that caused the lock-out can be found.

Filter and Registers

Is your filter clean? If there is too much air resistance, the furnace can trip out on a high temperature limit. Also check that the supply-air and return-air grilles are open and unobstructed.

Are all of your registers open?

You should have your furnace maintained annually by a qualified service technician.

You should change or wash your filters on a regular schedule. We recommend at least twice a year depending on the activity in your home. More often is better, once a month would be a maximum.

Keep the area around your furnace clean and unobstructed. Most gas and oil furnaces need combustion air to operate properly. These type of furnaces need access to air, preferably fresh air.

Keep the burner area of your furnace clean. If the flame on a gas furnace burns yellow, then the burners need cleaned. A yellow flame means incomplete combustion is taking place. Carbon monoxide is one byproduct of incomplete combustion. Carbon monoxide can be deadly in high enough concentrations.

Furnaces that require lubrication on the motors and bearings should be attended to by a qualified heating technician once a year.

Do not have anything combustible within six inches of your vent pipe.

Do not close off more than 20% of the registers in your house. This can cause high resistance and unnecessary heat build up in the furnace.

Do not store combustible material such as paint thinners, gasoline, etc. near your furnace.

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