A furnace that blows cool air is usually running the fan without making heat. Here is what to check, from the simple to the serious.
Check these first
- Thermostat fan set to On: the fan runs between heat cycles and blows room-temperature air. Set it to Auto.
- Thermostat set to Heat and above the room temperature
- Normal start-up: a few seconds of cool air before the burners warm the heat exchanger is normal
- Heat pump defrost: a heat pump briefly blows cooler air while it defrosts the outdoor coil
- Dirty filter causing an overheat shutdown
Problems that need a technician
- Igniter or flame sensor failure
- Blocked condensate drain tripping a safety switch
- Gas supply or gas valve problems
- Limit switch tripping from overheating
Real jobs
- Same-day igniter and flame sensor repair in Kearns
- No-heat call traced to a blocked condensate drain in Taylorsville
Furnace repair · No heat? What to check first · Our emergency line is answered live 24/7 at (385) 250-0687. Inside West Valley City limits, Monday–Saturday 8 AM–5 PM, we guarantee a technician within 45 minutes of answering your call, or the emergency inspection is free (terms).
Frequently asked questions
Why is my furnace blowing cold air?
Often the thermostat fan is set to On instead of Auto. Other causes are a dirty filter, a failed igniter or flame sensor, or a blocked condensate drain.
Is cold air from a heat pump normal?
Briefly, yes, during defrost. Constant cold air in heat mode is not.
When should I call for service?
If the thermostat and filter are fine and the air stays cold, call. Aegis’s emergency line is answered live 24/7.