Furnace Blowing Cold Air

A blower pushing unheated air around the house will drive the temperature down rather than up, so it's worth calling before the place gets colder.

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When this becomes an emergency

Every register is delivering air that feels cooler than the room.
The blower has been running nonstop with no warm air behind it.
There's a smell of unburned oil but no sound of a burner running.
The system runs its full cycle and the temperature never moves.

What a pro does

The first thing established is whether the burner is trying at all, because a burner that never attempts ignition and one that attempts and fails lead to completely different repairs. On oil equipment the usual path runs through the nozzle, the electrodes, the fuel filter, and the cad cell that proves the flame, any of which can leave the fan running while nothing burns. Fuel supply gets checked early too, since a tank drawn low takes in sediment and water that settles at the bottom, and moisture is a constant companion in coastal basements. Gas systems land in the same symptom by way of a fouled flame sensor or a lockout after failed tries. The reset button isn't the repair.

Frequently asked questions

What does the reset button on an oil burner actually do?

It clears a safety lockout so the burner will try again. Pressing it repeatedly floods the chamber with oil that isn't lighting, which is why one attempt is the sensible limit.

Can water in the fuel cause this?

It can. Condensation collects in tanks and settles below the oil, and water reaching the nozzle stops combustion cold while the rest of the system carries on as normal.

Why is there an oil smell if nothing is burning?

Unburned fuel sprayed into the chamber during failed ignition attempts has to go somewhere, and that odor is one of the clearer signs the burner is trying without succeeding.

Is it safe to leave the system running like this?

Running the fan does no harm, but leaving the thermostat calling while the burner fails over and over isn't doing the equipment any favors.

Furnace Blowing Cold Air?

Get connected with a local pro now.

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