Furnace Blowing Cold Air

When this becomes an emergency

• Air out of the registers feels cool even after the system has run for a while.
• The blower keeps running long past the point where the room should have warmed.
• You can hear the burner try to light, then hear it quit a second later.
• The system runs a cycle, gives no heat, then refuses to restart for several minutes.

What a pro does

Cool air out of the registers means the blower is doing its part while the heat source isn't. The technician watches a live cycle to see how far the sequence gets, because ignition that starts and then drops out looks nothing like ignition that never begins, and that distinction separates a dirty flame sensor from a failed ignitor or a gas valve that isn't opening. Lockouts get read next. Many boards store a fault code that says precisely which safety tripped and why the burner is being held off, so pulling that code beats guessing at parts, and on propane equipment a regulator that can't keep pressure up in extreme cold produces the same complaint without a single failed component in the system.

Frequently asked questions

Furnace Blowing Cold Air?

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