Why Your Furnace Blows Cold Air Then Shuts Off and How a Flame Sensor Might Be to Blame

It’s the middle of a Michigan winter, and your furnace suddenly starts blowing cold air for a minute before shutting off. You reset it, wait a bit, and it happens again. Sound familiar?

If so, the problem might be as simple — and as important — as a dirty flame sensor.

What Does a Flame Sensor Do?

Your furnace’s flame sensor is a small metal rod located near the burner assembly. Its job is to detect whether the gas burners have ignited properly. Once it “sees” the flame, it signals the control board to keep the gas valve open, allowing your furnace to continue heating.

If the flame sensor doesn’t detect a flame (often because it’s covered in dirt or soot), it will shut the system off within seconds — a crucial safety feature to prevent gas buildup.

That’s why your furnace may start, blow cold air for a short time, and then stop running altogether.

Signs Your Flame Sensor Is the Problem

If your furnace is cycling on and off quickly or blowing cold air, these are classic signs your flame sensor might be dirty or failing. Other indicators include:

• Furnace ignites briefly, then shuts off

• A flashing error code on your furnace panel

• You’ve replaced filters and checked the thermostat, but nothing changes

Why You Shouldn’t Ignore It

A faulty flame sensor may seem minor, but if ignored, it can cause repeated system shutdowns and unnecessary wear on components like the blower motor or igniter. More importantly, your home will struggle to stay warm — something no one wants in a Kalamazoo winter.

When to Call the Experts

If you’ve cleaned the sensor and the problem persists, it’s time to call the pros. At Douglas Heating Supply, our technicians can quickly test, clean, or replace the flame sensor and perform a full furnace check to ensure everything’s running efficiently.

We stock a full range of furnace parts, from flame sensors to igniters, control boards, and more so you can count on a fast repair and dependable warmth all season long.

Stay Warm With Douglas Heating Supply

Don’t let a faulty flame sensor leave you shivering this winter. Whether you need quick troubleshooting, parts, or full furnace service, Douglas Heating Supply has your back.

📞 Contact us today for fast HVAC repair in Kalamazoo and surrounding Michigan areas.

Live comfortable. Always.