Furnace Blowing Cold Air — Why & What to Do

Furnace running but only blowing cold air is one of the most common cold-weather calls we get in Salina. Nine times out of ten, it's one of six things — half of which you can check before you pick up the phone.

Check these first (safe DIY)

Before assuming the worst, verify these three no-cost items:

• Thermostat set to Heat (not just Auto) and fan set to Auto (not On — On runs the blower nonstop even between heating cycles).
• Air filter — a clogged filter can trip a safety limit that shuts off the burner but leaves the blower running.
• Circuit breaker at the panel — a tripped breaker for the furnace can cut power to ignition but leave the low-voltage blower call working.

The most common actual failures

If the above checks pass, one of these is likely — and all four need a technician:

• Flame sensor coated in soot — the furnace ignites for a few seconds then shuts down (repeats forever). Clean or replace the flame sensor; $150–$220.
• Failed ignitor — no ignition attempt at all, or clicking without flame. Common on 8+ year old furnaces; $175–$275.
• Pilot light out (older furnaces) — usually a bad thermocouple; $125–$200.
• Bad gas valve — rare but serious. $450+.

When to shut it off

If you smell gas, hear an unusual pop or boom on ignition, or the furnace short-cycles (turning on and off every 30-60 seconds), turn the thermostat to Off and call us. Short-cycling on a Kansas cold snap wears out the ignitor and heat exchanger fast.

Key takeaway. The first thing to check is always the thermostat mode, the filter, and the breaker — a lot of "cold air" calls end there. Anything past that is a same-day fix for a licensed tech.

Need a hand from a real Central Kansas technician? Call (785) 822-7550 and a Comfort Heating & Air tech will walk you through it — or request service online and we'll follow up the same business day.