Furnace Blower Runs all the Time

If your furnace blower runs all the time, your heating system is likely consuming large amounts of energy unnecessarily and experiencing unneeded wear. A furnace blower running all the time could require furnace repair to correct.

Troubleshooting a furnace blower running all the time

  • Check the thermostat to ensure the fan is set to off or auto, not on. If the fan on setting is selected, the blower will continue to run all the time, even if the furnace is not cycling.
  • The blower may be constantly running because the furnace is running. This may be the case if the thermostat’s current temperature is set above the current room temperature. Set the thermostat’s temperature lower than the current room temperature to trigger the furnace cycle to end – this should cause the blower to cease.

Issues causing a furnace blower to run all the time

  • The fan’s limit switch may have a manual option that overrides the fan control, causing the furnace blower to run all the time. If this switch has been set, this may be the source of a continuously running blower. You may be able to check for this yourself if you have a good working knowledge of your HVAC system components – otherwise, have your trusted heating technician check this for you.
  • Wires shorted out within your thermostat will prevent the stat from communicating effectively with the furnace. This could be to blame for a blower that constantly runs. Repairing or replacing the thermostat is necessary to solve this issue.
  • Wires within the fan’s limit switch may have shorted, causing the blower to continuously run. If this is the case, repair or replacement of the fan limit switch is necessary.