Gas furnace blowing cold air? Try these quick fixes

Nothing’s worse than turning on your gas furnace on a chilly day and feeling cold air blowing from the vents. But before you stress about expensive repairs, there are some common issues you can check on your own. Let’s dive into some quick fixes to get your home warm and cozy again.

Heads up: The tips in this article might not apply to your specific appliance model. We aim to provide helpful advice for all kinds of DIY appliance repairs, but differences in models and setups can lead to variations in troubleshooting steps, error codes, part replacements, and so on. For the most accurate guidance, it’s best to consult the manufacturer documentation for your specific appliance model or find your appliance’s model number here.

Make sure your furnace has power

Even though your furnace runs on gas, it still needs electricity to operate. A lack of power could be as simple as a tripped breaker or a flipped power switch.

1. Check the furnace’s power switch to make sure it’s in the “on” position.
2. Go to your electrical panel and inspect the circuit breaker. If the breaker for the furnace is in the “off” position, flip it back on.
3. Use a multimeter to check that the furnace is getting power. Test the voltage at the furnace’s power connection or outlet to confirm.

If power is restored, your furnace should start heating. If the breaker trips again, there may be a deeper electrical issue. 

Check your thermostat settings

The thermostat is often the first place to check when your furnace isn’t heating. If the thermostat isn’t set correctly, it can prevent the furnace from kicking on.

1. Make sure the thermostat is set to “heat” mode.
2. Adjust the temperature setting to be higher than the current room temperature.
3. If your thermostat uses batteries, replace them with fresh ones.
4. Reset the thermostat to see if it resolves the problem.

Replace dirty air filters

A clogged air filter restricts airflow, causing your furnace to overheat and shut off the burners. The result? Cold air blowing from your vents. Swapping out your air filter every 1-3 months can prevent this issue and improve your indoor air quality.

1. Locate the air filter compartment, usually near the blower or return air duct.
2. Gently remove the old filter by sliding it out.
3. Check the size printed on the filter frame and get a matching replacement.
4. Insert the new filter, making sure the airflow arrows point toward the furnace.
5. Close the filter compartment and turn the furnace back on.

Read more: 12 things you should know about portable space heaters

Check the gas supply

If gas isn’t reaching your furnace, it won’t produce heat.

1. Locate the gas shut-off valve near your furnace and make sure it’s in the “on” position (handle parallel to the pipe).
2. If other gas appliances aren’t working, inspect the main gas meter valve.

If you smell rotten eggs or hear a hissing sound, there might be a gas leak. Leave your home immediately and contact your gas provider.

Relight the pilot light

If you have an older furnace with a pilot light, a blown-out flame means no heat. Note: Newer furnaces use electronic igniters and don’t have a pilot light.

1. Turn off the furnace and wait five minutes to let any residual gas dissipate.
2. Locate the pilot light assembly with the gas valve.
3. Turn the valve to the “pilot” position.
4. Press and hold the reset button or gas control knob.
5. While holding it, use a long lighter or match to ignite the pilot light.
6. Continue holding the button for about 30 seconds after the pilot is lit, then release.
7. If the pilot light stays lit, turn the gas valve to the “on” position.

Read more: Your guide to choosing a space heater

Examine the blower motor

The blower motor is responsible for circulating warm air throughout your home. If the motor isn’t working, the furnace might be running, but you won’t feel any heat.

1. Listen closely to the furnace to see if you can hear the blower motor running. If you don’t hear it, it could be the issue.
2. Use a multimeter to check the motor for continuity. If the motor doesn’t have continuity, it’s faulty and likely needs to be replaced.
3. If the motor does have continuity, check the capacitor and wiring to make sure they’re not causing issues.

If the blower motor is the problem, it will need to be replaced to restore heating. If you’re unsure about testing electrical parts, we have more tips on using a multimeter in our repair help section.

Test the limit switch

The limit switch is a safety feature that prevents the furnace from overheating. If it’s faulty, it can stop your furnace from heating, even if everything else seems fine.

1. Look for the limit switch near the burner assembly or furnace compartment.
2. Use a multimeter to test the limit switch for continuity. If there’s no continuity, it may be defective and need replacing.
3. If the limit switch is tripped, it might be caused by a clogged filter or poor airflow, so make sure the air filter is clean and airflow is unobstructed before replacing the switch.

Read more: 12 simple space heater safety tips for this winter

Need more help?

Our repair help page offers detailed guides and videos on common furnace issues and fixes.

We’re here to support your DIY efforts with quality parts and expert advice.

Stay warm and comfortable, and let us know if you need any further assistance. Visit AppliancePartsPros.com for all your repair needs.

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