If your furnace suddenly starts blowing out cold air, it’s a sign that something is wrong with your heating unit. This is a problem that no homeowner should have to deal with, especially during the winter months when you need your centralized heating the most.
There are several causes for a furnace blowing cold air. Here are the most common causes and how you can fix them on your own.
1. Thermostat is On
Always check the thermostat first if you have a constant flow of cold air from the furnace. See if the fan is set to “on” or “auto.” If the fan setting is “on,” your furnace blower will keep running even if the air is not being heated. Switching it to “auto” makes the fan only blow air that’s been heated.
2. Clogged Air Filter
Air filters need to be cleaned regularly to keep your unit functioning properly. Dirty air filters can lead to a limited airflow in your furnace. If the airflow is restricted, your unit will work harder to heat your home until it eventually overheats. An overheated furnace will only produce cold air.
The solution: replace dirty air filters right away. Once the dirt blocking the airflow is removed, your furnace will go back to functioning normally.
3. The Furnace Hasn’t Warmed Up Yet
You may experience getting a blast of cold air when you initially turn on your furnace—and that’s normal. Similar to a hot water faucet, furnaces take time to warm up. The unit needs to push out cold air from the vents first before warm air is released. If warm air doesn’t come out after a few minutes, it’s time to schedule a visit from your trusted HVAC professional.
4. The Pilot Light is Out
Do you own an old gas furnace that’s blowing cold air? If so, then you might want to consider looking at its pilot light. Carefully check if the pilot light has gone out. If it has, then read the manufacturer’s instructions on how to safely re-light it.
If you’re not comfortable taking the DIY route to re-light, you have the option of calling your local utility company or an HVAC technician.
5. Dirty Flame Sensor
For pilotless ignition furnaces, the furnace is kept burning using a flame sensor. A dirty flame sensor could result in cold air being released from your unit. If you have experience with handling furnace components, you can clean the flame sensor on your own. This will restore the heating function of your furnace.
Are you still having problems with your furnace? If the above troubleshooting tips did not solve the issue, something serious could be happening with your unit. That’s when you need to call an HVAC professional to help you sort everything out. The cold air from your furnace could be caused by a faulty igniter, damaged circuit board, ductwork problems, and so on. These are complicated issues your HVAC technician can easily address.