While spring is nearly upon us, many Bay Area homeowners are still depending on their furnaces to keep their homes warm and comfortable. Unfortunately, there may come a time that your furnace starts blowing cold air through the registers, rather than warm air. So, what’s up? Here are the most common reasons the furnace might start blowing cold air.
Your thermostat is set to “on” instead of “auto.” When your thermostat is set to auto, your furnace will automatically kick on when the temperature drops below your desired temperature setting. However, when it’s set to “on,” the air will continue blowing through your registers, even when the furnace is not in a heating cycle. To remedy this, switch the thermostat to the “auto” position.
The heat has just kicked on. Just as it takes a bit for the water to get hot when you turn on the hot water faucet, it takes the air inside the ducts a few moments to warm when the air handler comes on. A brief period of cool air coming from the registers before warm air replaces it is normal.
The pilot light is out. Older furnaces are equipped with pilot lights, which may go out. If this happens, the gas that supplies the furnace’s burners is shut off by a device called a thermocouple. The furnace will blow cold air through the registers if the fan continues to run. If relighting the pilot light does not rectify the problem, contact a heat & air contractor.
A dirty flame sensor. Running your heat/air system with a dirty air filter can cause the flame sensor to become dirty over time, which may make the sensor incapable of detecting whether the burners on your furnace are lit. The flame sensor will shut the burners off if it detects they are not lit, causing cold air to come out of the registers. During a maintenance visit or twice-yearly tune-up, your technician will clean the flame sensor to ensure proper operation.
Malfunctioning limit switch. The limit switch basically tells your furnace fan when to kick on and shut off. If the switch malfunctions, it will result in cold air coming from your registers, as the furnace’s fan may not turn on or off. A malfunctioning limit switch should be inspected by a professional, who can determine if it can be repaired, or should be replaced.
As you can see, most of the reasons for a furnace blowing cold air aren’t all that serious. If you are experiencing problems and cannot determine what the problem is, contact the Bay Area heating and cooling experts at Ortiz Heating & A/C today for prompt, reliable service.