Furnace Exhaust Fan Runs Continuously

Follow the steps below to check the settings of your fan limit switch.

Furnace exhaust fan runs continuously. Keeping the fan on creates a more even distribution of heating and cooling circulating the air if you have cold or hot spots in your house like a bedroom above a garage. Remove the panel from your furnace and locate your fan limit switch. If the bad limit switch was locked in the closed position the exhaust fan would not turn on when was a call for heat and no signal to the control board preventing the furnace to turn on. This will cause the fan to automatically turn on.

Does the furnace work as normal aprt from the continuously running fan. At the furnace or air conditioner air handler or blower unit. Set incorrectly to manual or faulty and needs to be repaired replaced. Pull the white button out to reset your fan limit switch to auto.

Pros to running fan on air conditioner continuously. The electronic limit switches are disc shaped and mounted on the exhaust pipe at the furnace. One of the limit switches is locked in the open position so the fan runs continuously. If so your switch is.

Less frequent starts and stops of the fan can reduce the stress from startup and potentially help extend it s lifespan. But if the furnace fan runs continuously regardless of whether the furnace is heating or not your furnace fan limit switch is either. If your furnace goes off on high limit or if one of the rollout switches are open then the furnace fan will run all the time because the furnace control board is telling the furnace that the furnace has over heated and the fan runs to cool the furnace down. It does not control the fan directly.

Check to make sure the limit and rollouts are all closed. The fan limit switch may include a switch that manually. If that fan switch is set to man manual or on it will force the blower to run continuously. At the room thermostat.

The fan does have a pressure switch to prove to the micro that the fan is running for ignition to take place. The fan auto off or fan on off switch on the room thermostat should be checked. Check the small white button on the switch. This switch is located just under the furnace hood.