
Furnace Blowing Cold Air
Air moving without heat behind it means the burner side has quit while the fan carries on, so call before the house falls further behind the cold.
When this becomes an emergency
- Registers are moving plenty of air, but it's room temperature or colder.
- The burner tries to light, then gives up, and the fan keeps running anyway.
- The house temperature keeps sliding even with the system running nonstop.
- There's an oily or unburned-fuel odor near the registers after a failed start.
What a pro does
The fan working proves very little. What matters is whether the burner establishes and holds a flame, so a tech watches an entire start attempt from the beginning: call for heat, purge, spark, flame proving, then either steady operation or a lockout that explains itself. On oil equipment a worn nozzle, a clogged fuel filter, or an electrode that's drifted out of gap will spark without ever catching properly. Gas units usually point at a dirty flame sensor. Restricted return air matters too, because a filter packed with dust from an old cellar can push the unit into a high-limit trip that leaves the blower running long after the burner has been shut down.
Frequently asked questions
Furnace Blowing Cold Air?
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