Is your furnace blowing cold air instead of heating your home? Learn the most common causes and what to do next.
You turn on your heater expecting a wave of warm air but instead, it blows cold. For homeowners in Southern California, where furnaces are often unused for much of the year, this surprise is more common than you might think. Before you panic, here are some of the most frequent reasons your furnace is blowing cold air and what to do about it.
This is one of the simplest fixes. If your thermostat’s fan setting is switched to “On,” the blower will run continuously even when the furnace isn’t heating the air. Switch it to “Auto” so it only runs during active heating cycles.
When first starting up, your furnace may take a few minutes to begin pushing warm air. Give it a few minutes if it’s still cold after 5–10 minutes, further troubleshooting may be needed.
If you have an older gas furnace, the pilot light might have gone out. This prevents the burners from igniting, which means the air never gets heated. Relighting the pilot is usually a simple fix but if it keeps going out, call a professional.
Airflow restrictions caused by a clogged filter can cause the furnace to overheat, triggering a safety shutoff. In this case, the system might continue to blow cold air. Try replacing the air filter and restarting the system.
The flame sensor detects whether the burners are lit. If it’s dirty or malfunctioning, it may shut off the gas supply even when there’s no danger leaving your furnace blowing cold. This is a common issue in coastal areas like Orange County due to higher humidity and dust.
In some cases, the furnace may be working properly, but the heated air is escaping through leaks or disconnected ducts before it reaches your vents. This is more likely in older homes or if rodents have damaged the ductwork in the attic or crawlspace.
Some furnaces have safety mechanisms that detect overheating and shut off the burner. While the blower continues running (to cool the unit), only cold air comes out of your vents. This could be caused by dirty filters, closed vents, or internal mechanical issues.
If you’ve tried changing filters, checking the thermostat, and verifying airflow, but the problem persists it’s time to call a licensed technician. Ignoring these issues can lead to costly damage or even gas leaks.
If your furnace is blowing cold air during chilly mornings or evenings, don’t wait for the problem to get worse. Call our certified HVAC specialists at (949) 229 6766 or book a service call online today. We proudly serve homeowners throughout Orange County and the greater Los Angeles area fast, affordable, and reliable.
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(949) 229 6766