How to Troubleshoot a Forced Air Heating System

When your heater doesn't work on those cold winter nights, knowing how to troubleshoot it can help to get it running again. A forced air heating system employs a heat exchanger warmed by flame and then uses a fan to circulate the warmed air throughout the home. A thermostat sets the desired temperature and controls the heating and fan until the set temperature is reached. Run through a few basic troubleshooting techniques that could include incorrect thermostat settings, tripped breakers, blown fuses and defective fan motors. For more complex problems, call in a qualified service technician.

Use a forced air heating system to warm your home or office.
  1. Check the thermostat selection switch is set to "Heat" if the system does not turn on. Set the temperature at least three degrees above the current room temperature. Check to ensure batteries are charged and the display is showing, if the thermostat is electronic. Switch on the fan. Listen for the furnace fan to engage. If you do not hear the fan engage, place your hand in front of one of the air registers. If you do not feel air blowing, there may be no power to the system.

  2. Inspect the household electrical panel for tripped breakers or blown fuses. Reset the breakers by flipping them up and down a few time until they click into place. Replace blown fuses with others of the same amperage rating. Look for the emergency shut-off switch next to or nearby the furnace. Verify that it is on. The emergency shut-off switch resembles an ordinary light switch.

  3. Check to see that the furnace door or service panel is fully closed. The cutout switch can sometimes engage when the service panel is open.

  4. Adjust the anticipator if the system runs constant short heating cycles. Lift the cover from the thermostat and locate the anticipator. The anticipator is a thin, pointed dial. Move the anticipator to a higher level if it is set to .2 or lower. Move the dial up to the .3 to .4 range. This action should correct the short cycling. Consult your owner's manual for more detailed information on what range to set the anticipator for your particular brand of forced-air heating system.

  5. Move the fan switch on the thermostat from "Auto" to "Manual" or "On" if the blower fan does not engage. Check for loose wire connections on the fan motor if the fan does not engage instantly. If this is not the problem, the motor could be defective. Have a qualified service technician investigate this further.


  • If the circuit breaker keeps tripping, or the fuses continue to blow, have a qualified service technician investigate the problem for you.
  • If you are uncomfortable dealing with gas systems, call in a qualified service technician.
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