When the furnace quits on a freezing New Jersey night, it's tempting to panic. But some no-heat problems have simple causes you can check yourself in a few minutes. Work through this list before you call — and know the signs that mean it's time to bring in a licensed technician.
Check the thermostat
It sounds obvious, but confirm the thermostat is set to HEAT and the target temperature is above the current room temperature. Replace the batteries if it's a battery model — dead batteries are a surprisingly common cause of 'no heat' calls.
Check the power and switch
Furnaces have a standard wall switch nearby that looks like a light switch. Make sure it wasn't flipped off accidentally. Then check your breaker panel for a tripped furnace breaker.
Check the air filter
A clogged filter restricts airflow and can cause the furnace to overheat and shut down as a safety measure. If your filter is gray and packed with dust, replace it and try again.
Check the furnace door
Most furnaces have a safety switch that prevents operation if the access panel isn't fully seated. If someone recently changed the filter, make sure the panel is snapped firmly in place.
Check the gas supply
If you have other gas appliances, confirm they're working. If none have gas, the issue is with your supply, not the furnace, and you should contact your utility.
Pro Tip
If you ever smell gas, don't troubleshoot — leave the house and call your gas utility and a licensed technician from outside.
When to call a professional
Call a licensed heating technician if the furnace still won't fire, cycles on and off rapidly, blows only cold air, or makes banging or screeching noises. These point to issues like a failed igniter, flame sensor, blower motor, or gas valve — repairs that require proper tools and training to do safely.
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