Why Your Furnace Might Be Blowing Cold Air & What to Do About It

There’s nothing worse than turning on your heat during a Minnesota winter and feeling a blast of cold air. If your furnace is blowing cold air—or heating unevenly—don’t panic. Brent’s Heating & Cooling is here to help you understand what’s going on and what you can do before calling for professional HVAC service.

Common Reasons Your Furnace Is Blowing Cold Air

1. Your Thermostat Isn’t Set Correctly

It sounds simple, but thermostat issues are one of the most common causes. Make sure your thermostat is set to “Heat” and the fan is set to “Auto,” not “On.” When it’s on “On,” the blower runs constantly, pushing out air even when the furnace isn’t actively heating.

2. Dirty or Clogged Furnace Filters

In Duluth, Carlton, and surrounding Minnesota areas where furnaces run hard all winter, clogged filters are a frequent culprit. A dirty filter restricts airflow, which can cause your furnace to overheat and shut down its burner—leaving you with cold air.

Fix: Replace the furnace filter every 1–3 months, especially during heavy winter use.

3. Pilot Light or Ignition Problems

Older furnaces use pilot lights, while modern systems use electronic ignition. If either fails, the furnace can’t heat the air before blowing it through your vents.

Fix: Check for a lit pilot light. If it keeps going out or the ignition system is clicking but not lighting, it’s time to call an HVAC technician.

4. Overheating Furnace

If your furnace keeps overheating, it may shut off the burner as a safety precaution—resulting in cool air. Overheating often happens due to airflow issues, dirty components, or mechanical problems.

Fix: Replace your filter, check vents for obstructions, and schedule a professional furnace inspection.

5. Ductwork Leaks

Leaky or uninsulated ducts can cause warm air to escape before it reaches your living spaces, creating uneven heating or cold rooms. Homes in Carlton, Cloquet, and the Duluth area with older duct systems experience this frequently.

Fix: Have your ductwork inspected, sealed, and insulated to improve both comfort and efficiency.

6. Furnace Flame Sensor Issues

The flame sensor ensures your furnace is burning gas safely. If it’s dirty, the system may shut off prematurely—leading to cold air blowing through your vents.

Fix: A technician can clean or replace the flame sensor quickly and safely.

Why You Might Notice Uneven Heat

Cold rooms and inconsistent temperatures are also common winter complaints. These issues may be caused by:

• Blocked or closed vents
• Poor duct design or leaks
• Low insulation levels
• A furnace that’s improperly sized for your home
• Thermostat placement issues

Homes across St. Louis County, Pine County, and Lake County often experience uneven heating due to older ductwork or changing insulation levels over time.

When to Call a Professional

If your furnace continues blowing cold air after checking basic settings and changing the filter, it’s time to call Brent’s Heating & Cooling. We provide fast, reliable furnace repair throughout Carlton, Duluth, Cloquet, and surrounding areas—especially during no-heat emergencies.

Stay Warm with Brent’s Heating & Cooling

As a trusted HVAC company serving Northeast Minnesota since 2003, Brent’s Heating & Cooling delivers expert furnace repair, installation, and maintenance to keep your home comfortable all winter long. From uneven heating to cold air issues, our technicians can diagnose the problem and get your heat back on quickly.

Need furnace repair near you in Carlton, Duluth, or Cloquet?
Call us at (218) 390-1479 or request service at Brent’s Heating & Cooling.

Stay warm, stay safe—and don’t hesitate to reach out if your furnace is blowing cold air or giving you trouble this winter!