What causes a heater fan to keep running

fansheating

I have a regular gas air heater that heats the whole house. It is installed in a garage.

When I use thermostat to turn on the heat it works as expected. When temperature reaches set value the gas turns off.

But the fan keeps running, cycling room temp air around. It never turns off. I waited at least an hour.

I replaced a thermostat. Same problem.

Best Answer

There should be a switch on the thermostat that says "ON AUTO", make sure it's set to AUTO.

If the switch is set to auto, but the fan continues to run. You may have a short between the R wire and the G wire, or a problem with the control board in the furnace.

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