Why Is My Furnace Blowing Cold Air? Common Causes & Fixes

Is It Time for a New Furnace Installation? Find Out In This Article

When the weather turns cold in Issaquah and across the Pacific Northwest, your furnace becomes one of the most important systems in your home. But what happens when you switch it on and discover the vents are blowing cold air instead of heat?

It’s a frustrating experience, but it doesn’t always mean your furnace is failing. Here are some of the most common reasons for cold air and how to know if it’s a quick fix or time for a new furnace installation. 

MORE ON FURNACES: Bob’s Heating Offers High-End Furnace Services for Your Winter Season

Issue 1: Thermostat Settings

Sometimes the issue starts with the thermostat. 

If the fan is set to ON instead of AUTO, your blower will keep running even when the furnace isn’t heating. That means you’ll feel room-temperature air blowing through the vents.

Fix: Switch the fan setting to AUTO so warm air only circulates when the furnace produces heat. If the settings are correct and the system still isn’t heating, schedule a professional inspection.

Issue 2: Dirty Air Filters

Clogged filters block airflow and can cause the furnace to malfunction. When that happens, the safety system may shut down the burners, leaving the blower to push out cold air or no air at all.

Fix: Replace or clean filters every one to three months, depending on your system and household needs. If you’re unsure what filter size to use, Bob’s Heating can recommend the right fit and even set you up with our filter replacement program.

Issue 3: Pilot Light or Ignition Issues

Gas furnaces rely on a pilot light or electronic ignition system to start the burners. If the pilot light goes out or the igniter fails, your furnace won’t heat properly, and you’ll only feel cold air coming through the vents.

Fix: First, make sure your gas supply is on. If the pilot light won’t stay lit or the igniter isn’t sparking, it’s time to call a professional. Working with gas and ignition systems can be dangerous, and a trained technician should always handle furnace repairs.

Issue 4: Clogged Vents or Ductwork Leaks

If certain rooms are getting warm air while others aren’t, you may have blocked vents or leaking ductwork. Over time, dust, debris, or even pests can interfere with airflow. Leaks in the ductwork can also pull in cold air from crawl spaces or attics.

Fix: Start by checking that all supply vents are open and unobstructed. If the problem persists, schedule a duct inspection. Sealing leaks and cleaning ducts improves airflow and efficiency.

Safety Concerns and When to Call a Professional

Call a professional immediately when your furnace isn’t igniting properly, shuts down repeatedly, or you notice unusual smells or sounds. These symptoms can point to gas leaks, electrical failures, or other safety hazards. Bob’s technicians are trained to diagnose and resolve these issues quickly and safely.

Prevent Problems With Seasonal Maintenance

Regular furnace maintenance can help homeowners avoid most cold-air problems. A professional tune-up in the fall ensures your heating system is clean, efficient, and ready for heavy use during winter. Seasonal maintenance also extends the lifespan of your equipment and helps prevent expensive emergency repairs.

Take Advantage of Our Pre-Season Furnace Sale

If your furnace is showing signs of age or has repeatedly had issues, it might be time for an upgrade. Through the end of November, Bob’s Heating is offering special savings during our Pre-Season Furnace Sale. It’s the perfect opportunity to replace an aging system before winter temperatures settle in.

Call 1-800-840-3346 or visit our promotions page to learn more and schedule your installation.