Furnace Blower Not Working, Loud, or Won't Shut Off
A fan that runs nonstop can be a thermostat setting. Grinding, squealing, a burning smell or smoke mean switching the furnace off and leaving it for a professional.
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What to do right now
Smoke, fire or a CO alarm? Get out
Get everyone out and call 911 from outside. Don't stop to switch anything off.
Fan running nonstop? Check the fan setting
On the thermostat, a fan set to On runs all the time. Set it to Auto so it runs only with the heat.
Fan won't run? Check the switch and breaker
Make sure the furnace switch is on. If the furnace breaker has tripped, reset it once, standing on a dry floor. If it trips again, leave it off. Carrier says a technician should inspect repeated tripping, to prevent fire hazards.
Shut the blower door properly
Trane's guide asks whether the blower compartment door is in place. Close it fully.
Change a dirty filter, power off first
Switch the furnace off at its switch before you slide the old filter out.
Grinding, squealing or a burning smell? Switch it off
Turn the furnace off at its switch and leave it off. Carrier calls smoke or a burning smell urgent warning signs. Call a professional rather than running it to see if the noise stops.
Never bypass the door switch
Never tape down or hold in the switch behind the furnace door. Leave the inside of the furnace to a professional.
The motor, capacitor and wiring are behind that door. Carrier's advice on the capacitor is plain: do not touch it.
Furnace blower not working: what is happening
The blower is the fan that pushes warm air through the ducts. It needs power, a closed door, and a signal from the thermostat.
Carrier's guide names the thermostat fan setting as the most common cause of a furnace blowing cold air. Left on On, the fan also runs nonstop.
Furnace blower is loud: when to switch off and when to leave
- Grinding or squealing: switch the furnace off and call a professional.
- Burning smell: switch it off and leave it off.
- Smoke or flames: get everyone out and call 911 from outside.
- The breaker trips again after one reset: leave it off for a technician.
- CO alarm or a gas smell: leave first, then call 911 and ATCO from outside.
Furnace blower running constantly or dead: what a pro handles
Carrier says repairing or replacing a blower motor involves high-voltage electrical wiring and is generally best left to a professional HVAC technician. The capacitor sits in the same compartment. That's why the steps on this page stop at the door.
Questions
Why does my furnace blower hum but won't start?
The cause can't be read from here, and the parts involved sit behind the blower door. Turn the furnace off at its switch. Don't open the compartment to look; Carrier warns that blower motor work involves high-voltage wiring.
Why is my furnace blower running constantly?
Check the thermostat first. A fan set to On runs whether or not the furnace is heating; Auto runs it only when heating. If it's on Auto and still won't stop, leave it for a professional.
Why does my furnace blower keep running with no heat?
A clogged filter is one cause. Carrier explains that a dirty filter can trip the high-limit switch, which stops the burners while the fan keeps running. Switch off, replace the filter, and switch back on. If the air stays cold, see furnace blowing cold air.
What does a high-pitched noise from the furnace blower mean?
Treat squealing from the blower as a signal to stop. Switch the furnace off at its switch, leave the panel closed, and have a professional inspect it.
Why is my furnace fan not turning on for heat?
Run the basic checks: thermostat on Heat with the fan on Auto, furnace switch on, breaker reset once at most, blower door fully closed. If the fan still doesn't start, it's a job for a professional. Keep the furnace off if you smell anything burning.
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