Furnace Not Blowing Hot Air? Here’s Why
With winter just around the corner, keeping your home warm and cozy is a top priority as the temperatures drop. That’s what your furnace is for—just turn it on, and it should heat your home. At least, that’s the idea. But what if you turn on your furnace and discover it’s blowing cold air instead? That won’t do much to keep your family warm, and you’ll want answers fast to get things back on track.
Is your furnace or heater not blowing hot air? You’re in the right place. Here, we’ll walk you through 7 potential reasons your furnace might not be working properly—and when it’s time to call in the professionals.
Incorrect Thermostat Settings
If you notice your furnace is blowing cold air, the first thing you should do is check your thermostat. While this seems obvious, your furnace can blow cold air if the thermostat setting is wrong. You’ll want to check the fan setting as well. If your fan is set to “on,” then it will blow air continuously throughout your home, making the air feel cold. Try switching the fan setting to “auto” and see if that helps.
If this doesn’t fix the issue, check the temperature setting on your thermostat. It should be set to a temperature that’s higher than the current reading in your home. If it’s lower, make the necessary adjustments to reset the temperature.
After changing the fan and temperature settings, the last thing you can check is your thermostat’s batteries. Low or dead batteries can lead to improper temperature control, so change the batteries and see if that fixes the problem.
Dirty Filter
Do you remember the last time you changed the air filters on your furnace? If the most recent filter change was months or years ago, this may be the issue as to why your furnace isn’t blowing hot air.
HVAC air filters catch particles such as dust and allergens before they circulate throughout your home, making your air cleaner. Over time, these filters can get so full of dust and debris that airflow is limited in and around your furnace.
Luckily, this is an easy fix. Take out the filters in your furnace and hold them up to a light. You should be able to see some light passing through the filter. If you can’t see any light, this means the filter is full, and it’s time to replace it. Look at the size of the filter and make sure you replace it with the same size to ensure proper airflow.
You should change your air filter every 6 months. If you have pets or more traffic in your home, you may need to do it more frequently. Check your filters once a month to see if you need to replace them.
Pilot Light Issues
Gas furnaces use a pilot light to ignite the heater and warm the air. This light is meant to stay on at all times, but sometimes it can get blown out by accident. If you recently had maintenance done on your furnace, the pilot light may have been snuffed out. The first thing to do is check your furnace ignitor and see if the pilot light is on. If it’s off, you may be able to relight it yourself. Check your furnace’s manual to see how to safely relight it.
If you relight the pilot light and it goes out again shortly after, it could be dirty. A buildup of dust and other debris can prevent your pilot light from staying lit. You can clean off any debris you see and try relighting it again.
If the light goes out again after cleaning it, the last thing to check is the gas supply line. Make sure the line is open and your furnace is getting a consistent supply of gas.
Ducts are Leaking
The ducts in your home are what carry the warm air from your furnace to the vents throughout your home. Over time, these ducts can get worn down from daily use. This can lead to cracks or damage that cause outside air to mix with the warm air from your furnace. Cold air can seep in, and your warm air can leak out, leading to the air from your vents feeling cold.
Damage and weak spots in your ductwork can go unnoticed until you turn on your furnace and feel cold air. You can have an HVAC professional inspect your ducts and check for any damage or weak spots that can be letting in cold air.
Low Fuel Supply
Whether you have a gas, electric, or oil furnace, they all run off a fuel source to keep them running properly. Without fuel, your furnace may start to blow cold air without producing any heat.
- Gas Furnace: A gas furnace can’t produce heat if it doesn’t have gas to burn. Check that your gas valve is open and your furnace is getting the gas it needs.
- Electric Furnace: An electric furnace won’t run without power. If your furnace is not running at all, check for a blown fuse or breaker.
- Oil Furnace: Oil furnaces need to burn oil to produce heat. Check to see if the oil tank is empty and if your furnace has enough fuel to run.
Old or Dirty Flame Sensors
Your furnace has a built-in flame sensor that turns it on and off depending on if there’s a flame present. This prevents gas from traveling through your vents and into your home. Over time, this sensor can become faulty and give false signals to the furnace. A buildup of dirt and grime can also cause the sensor to malfunction, leading to your furnace turning on and off repeatedly.
If the flame sensor shuts off your furnace, the fan may keep chugging along. This filters cold air throughout your home rather than the warm air you want.
Furnace Is Overheating
If your furnace is not blowing warm air, it could be that it’s overheating. Your furnace could be overheating for a variety of reasons, such as needing to replace your filters. As your furnace gets older, parts can begin to wear down and become less efficient.
If you suspect your furnace is overheating and you’ve tried the previous options with no success, contact an HVAC expert to take a look. The issue could be serious enough that you don’t want to risk trying to fix it yourself. Leave it to the professionals who know what they’re doing.
When Should You Call a Professional?
Your furnace and HVAC system consist of a ton of different parts that all work together to keep your home warm. When your furnace isn’t doing its job, there could be one of many causes. You can do basic at-home fixes such as replacing filters, adjusting the thermostat, and checking your furnace’s fuel source. Any other repairs need to be left to the professionals.
Semper Fi Heating & Cooling offers furnace repair services to get your home warm in time for winter. Our team will work with you to get to the root of the issue and get your furnace back up and running in no time. We also offer maintenance services to help prevent these issues from happening in the first place. We’re proud to serve our local communities in the Phoenix and Las Vegas areas.
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