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Heating · Minnesota

Furnace Blowing Cold Air

Cool air at the registers means the fan side is fine and the burner side quit, which is worth sorting before the house falls behind in hard cold.

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When this becomes an emergency

What a pro does

When cold air comes out of the vents, the blower is doing its job and the burner isn't. A technician watches a full call for heat from the beginning: does the inducer spin up, does the pressure switch prove, does the ignitor glow, and does the flame sensor confirm what the burner just did. On sealed-combustion units the sidewall intake and exhaust matter enormously, since drifted snow or a frosted-over termination can starve the pressure switch and stop ignition cold. Soot or scale on the flame sensor is the most ordinary answer of all. Forcing a unit past a lockout is never the fix.

Frequently asked questions

Sealed-combustion equipment breathes through a pair of plastic pipes on an outside wall. Drifted snow or a rime of frost across either one is enough for the safety circuit to refuse ignition.
Indirectly. A choked filter usually shows up as weak airflow first, but the overheating it causes can trip a limit that shuts the burner while leaving the fan running.
The fan alone won't damage anything. Leaving the thermostat demanding heat through dozens of failed ignition attempts is harder on the ignitor than it's worth.
It often does. A marginal flame sensor or a partly restricted vent tends to fail on the coldest nights and behave perfectly the afternoon someone shows up to look at it.

Furnace Blowing Cold Air?

Get connected with a local pro now.

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