Why is My Furnace Blowing Cold Air?

Monaca is known for having long and cold winter seasons. Furnaces are a popular and affordable heating option. One of the most frustrating problems homeowners experience is a furnace blowing cold air.

Thermostat Problems

If your furnace seems to be blowing cold air, one of the first places to start is the thermostat. Check that it’s set to HEAT, not COOL, and that the temperature is higher than the room setting. Also confirm the blower fan is set to AUTO rather than ON.

Unfortunately, if you set the blower fan to ON, it will run around the clock. Any time that your furnace shuts off, the blower fan will continue to run. It will circulate cooler air throughout your vents, which can seriously impact the comfort of you and your family. If you have your blower fan set to ON, you need to switch it back to AUTO. This will ensure that your blower fan is only operating whenever your furnace is running.

Dirty Air Filter

One culprit you may not think of when it comes to your furnace blowing cold air is a dirty air filter. Unfortunately, when the air filter is clogged full of dust and other debris, it can restrict airflow throughout your ducting. When this happens, the inside of your furnace will start to overheat.

Your furnace has a built-in limit switch that’s responsible for kicking your furnace off whenever it experiences overheating. This helps prevent a fire hazard in your home and protects the internal components of your heating system. It’s important to note that the limit switch only shuts off the furnace and not your blower fan. Your blower fan will continue to run through the full cycle, circulating cool air.

Fortunately, you can easily fix this problem by diagnosing your air filter. You want to pull it out of its housing and hold it up to a light. If you can’t see through the filter, you need to replace it with a new one. It’s recommended that you check your air filter every month and replace it whenever necessary. Most homeowners find they need to replace their air filter every two to three months.

Flame Sensor Malfunction

Fuel-burning furnaces have an integrated flame sensor that’s responsible for providing optimal system safety. The sensor detects when there’s a flame on the burner. Whenever there’s a flame, it will allow adequate fuel to flow to the burner to create heat. However, if it doesn’t sense a flame on the burner, it will automatically shut off the fuel supply. This is to prevent a buildup of toxic fumes inside your furnace.

Unfortunately, if your flame sensor is malfunctioning, it could falsely detect that there’s no flame on the burner when there really is. It could cause your unit to shut off as a safety precaution while still allowing the blower fan to run. This is another case where the blower fan will circulate unheated air throughout your home instead of warm air.

There are typically two different problems that a flame sensor can have. One common issue that many homeowners encounter is that the sensor eye is covered in grime or soot. When this happens, it obstructs the flame sensor from viewing the live flame on the burner. Typically, cleaning the sensor eye is all that’s needed to restore functionality to the unit. The other problem is when the flame sensor itself is faulty. This requires professional furnace repair to replace the flame sensor with a new one.

Faulty Limit Switch

Having a limit switch on your furnace provides extra peace of mind when it comes to dealing with fire hazards and toxic fume buildups. Its main job is to prevent these from happening by shutting off your equipment when overheating occurs. However, just like any other component of your furnace, limit switches are prone to malfunctioning.

If your limit switch malfunctions, it can cause your furnace to shut off while still allowing the blower fan to run through the full cycle. This is another instance where you need a professional to diagnose the limit switch and replace it with a new one.

A Note About Furnace Maintenance

There are many things you can do as a homeowner to greatly minimize your risk of needing furnace repair service. One of the most important things is getting an annual furnace tune-up. This is where one of our professionals comes out and performs in-depth maintenance service on your system.

Expert Furnace Repair Service

BVSM Heating & Air Conditioning is your go-to expert for prompt furnace repair in Monaca, PA. We can also assist with all your furnace maintenance, installation, and replacement needs.

Contact our office today to book your next repair service in Monaca.