1. The Furnace Just Started Up — Give It a Minute
When your furnace first turns on, it has to push out any cool air sitting in the ducts before the warm air reaches your vents. This usually takes a few minutes.
What to do:
- Wait 3–5 minutes after the system starts.
- If warm air follows shortly after, you’re good — no repairs needed.
If it keeps blowing cold air after that, move on to the next steps.
2. Your Thermostat Might Be Set Incorrectly
This is more common than you’d think. Sometimes the thermostat is accidentally set to “ON” instead of “AUTO.”
When it’s on “ON,” the blower fan runs continuously — even when the furnace isn’t heating — so it pushes room-temperature air through the vents.
Check this:
- Make sure the thermostat is set to
AUTO.
- Confirm it’s in
HEAT mode and set a few degrees higher than your current room temperature.
3. The Furnace Filter Is Dirty or Clogged
A blocked air filter can restrict airflow, causing the furnace to overheat and automatically shut off the burners for safety. The fan continues to run, but it only blows cool air.
How to fix it:
- Turn off your system.
- Remove the air filter and check if it’s dirty or gray.
- Replace it with a clean one (check your owner’s manual for the correct size and type).
Pro tip: Replace or clean filters every 1–3 months — especially during heavy heating use in fall and winter.
4. Pilot Light or Ignition Problems
If you have an older gas furnace with a pilot light, it may have gone out.
For newer models with electronic ignition, dirt or a faulty sensor can prevent the burners from lighting.
What you can do:
- Check to see if the pilot light is burning steadily (blue flame).
- If it’s out, follow your furnace’s relighting instructions — or call a technician if you smell gas or aren’t comfortable relighting it.
5. The Furnace Is Overheating
If the system runs too hot — often because of restricted airflow or internal issues — it will shut off the burners as a safety measure while the fan continues to blow.
You’ll notice:
- Warm air for a short time, then suddenly cold air.
- Furnace restarting repeatedly (short-cycling).
This usually requires professional attention to inspect the limit switch or airflow system.
6. Duct Leaks or Damaged Vents
If you feel warm air in some rooms but cool air in others, you might be losing heat through duct leaks in your attic or crawl space.
Leaky ducts waste up to
30% of your heated air, which means higher bills and uneven comfort.
How to fix it:
Schedule a
duct inspection and sealing service. Mayster Heating & Air uses specialized tools to locate leaks and seal them, improving efficiency and comfort.
7. Your Furnace Needs Professional Attention
If you’ve checked all the above and your furnace still blows cold air, it’s time to call a professional technician. You could be dealing with:
- Faulty gas valve or control board
- Dirty flame sensor
- Broken ignitor
- Thermostat wiring issues
- Blower motor malfunction
A trained HVAC professional can safely test, diagnose, and repair the issue so your system runs properly again.
How Mayster Heating & Air Can Help
Our certified technicians handle
furnace repairs, tune-ups, and replacements across
Pierce, King, Kitsap, and Thurston Counties. We respond quickly, explain the issue clearly, and make sure your home stays warm, efficient, and safe.
Whether it’s a simple filter change or a full heating system service, we’re here to help — no surprises, just reliable work you can count on.
Ready to Get Your Heat Back?
Don’t let cold air ruin your comfort.
Call
(206) 492-4215 today to schedule a furnace inspection or repair.
