Why Is My Furnace Blowing Cold Air?

One of the most frustrating things you may deal with during the wintertime is cold air coming out of your ductwork. There are actually a few different reasons why this may be happening with your furnace. It’s important to do some basic troubleshooting and know when to contact a professional for further assistance.

Understanding Normal Furnace Operation

One of the first things to understand, when it comes to the functioning of your furnace, is that the blower fan typically kicks on before it starts heating. This means that your blower fan can be circulating lukewarm air throughout your home that you may perceive as being cold. This happens for about one to two minutes until your heating system starts producing heat. If you notice just a brief period of cold air before it heats up, it’s likely the normal functioning of your furnace.

Clogged Air Filter

One common reason that your furnace may start to blow cold air instead of warm air is a clogged air filter. Your system’s air filter is responsible for removing unwanted airborne debris from your home. Unfortunately, if the filter gets too dirty, it can act more like a wall than a filter system. 

To solve this issue, all you need to do is replace the dirty air filter. You can verify that your filter is dirty by holding it up to a light. If you can’t see through it, it’s time for a replacement. We recommend checking your filter monthly. Most homeowners find they need to replace their filter every two to three months.

Incorrect Thermostat Setting

Another reason that your vents may be producing air that feels cold during the winter months is that you have your thermostat set incorrectly. On your thermostat, there’s a setting for the blower fan. You can have it set to on, off, or auto. If you set your fan to auto, it will only turn on whenever your furnace turns on. However, if you set it to on, your blower fan will run nonstop.

This means that it will blow hot air when your furnace is running. However, it will circulate the air already in your home when your furnace is off. Many homeowners perceive that air as being colder because it’s a lower temperature than the hot air that your furnace produces. You can easily remedy this issue by setting your blower fan to auto instead of on.

Ignition Problems

Another reason it may feel like cold air is coming out of your furnace vents is due to ignition problems. For your furnace to ignite, it needs to have a spark sent from the electric igniter to the burner. If that doesn’t happen, your furnace won’t be able to produce heat. However, it will still have its blower fan operating.

The blower fan will simply circulate air throughout your home without heating it. When you have an ignition issue, your furnace is likely to experience short cycling. This is where it repeatedly cycles on and off. It’s necessary to have one of our professional HVAC technicians further evaluate and repair your furnace.

Overheated Furnace

Another potential culprit behind why your furnace isn’t producing hot air is overheating. Furnaces have a built-in safety mechanism that shuts the furnace off in the event of excessive temperature. This prevents the sensitive internal components of your furnace from damage and reduces your risk of an electrical fire. When your furnace starts to overheat, it will automatically shut off. However, its blower fan will continue to run through the cycle.

This will circulate stale air throughout your home instead of producing hot air. There are several different reasons that your furnace may overheat. These include a dirty air filter, blocked vents, blower motor malfunctions, and a cracked heat exchanger. You’ll need a professional technician to handle issues other than a dirty air filter.

Ducting Issues

One other culprit that may be to blame for cold air coming out of your ducting in winter involves ductwork. Your furnace may be operating perfectly fine. However, if there’s an obstruction or a leak in your ductwork, that hot air may not make it to the rooms in your home. If you have a large leak in your ducting, the hot air will escape into your wall or floor cavities.

If there’s a blockage in your ductwork, like a pest nest, air can’t travel through it. You’ll need a professional evaluation to determine the issue you have and to remedy it successfully.

Expert Furnace Repair Service

Hometown Plumbing, Electrical, and HVAC provides expert furnace repair services for homes in Johnson City, TN. We can also help with all your furnace installation, replacement, and maintenance needs. Just phone our office today to schedule a service appointment with one of our HVAC technicians.