Heating
Why Is My Furnace Blowing Cold Air?
The most common reasons a furnace blows cold air in a Wisconsin winter, what you can safely check yourself, and when to call for repair.
Check the thermostat fan setting
If the fan is set to ON instead of AUTO, the blower runs constantly — even between heating cycles — and you'll feel cool air from the vents. Switch it to AUTO and see if the air warms up once the burners light.
Look at the air filter
A badly clogged filter chokes airflow. Many furnaces will overheat and shut the burners off as a safety measure while the blower keeps running, which pushes out cool air. Swap the filter and give it a few minutes.
Ignition or flame sensor problems
Modern furnaces use an igniter and a flame sensor. If the sensor is dirty or the igniter is failing, the furnace tries to start, can't confirm a flame, and shuts the gas off. This is one of the most common no-heat calls we get, and it's usually a quick fix for a technician.
Blocked intake or exhaust pipes
High-efficiency furnaces vent through white PVC pipes on the side of the house. Snow drifts and ice can block them, and the furnace will lock out for safety. Gently clear snow away from the pipes — never force anything off a frozen pipe.