You’re inside your home, beginning to shiver as the temperature outside dips lower and lower. So you go to turn on your furnace, looking forward to your furnace blowing hot air.
Instead, you’re greeted by the furnace deciding to blow cold air. That’s not right – so what’s going on? Do you need emergency furnace repair or Toronto furnace installation? Read ahead to find out!
It’s important to note that these are potential causes, and a thorough inspection by a qualified HVAC professional is necessary to accurately diagnose and address the issue.
Common Reasons For Furnaces Blowing Cold Air:
- Your Furnace Isn’t Warmed Up Yet
- Your Thermostat is Set Incorrectly
- The Furnace Filter is Dirty
- Your Furnace Has Overheated
- The Condensate Line is Clogged
- The Pilot Light Keeps Going Out
- There’s A Problem With The Gas Supply
- The Air Ducts Are Leaking
- The Coils are Clogged
- The Air Vents are Blocked
- The Heat Exchanger is Cracked
1. Your Furnace Isn’t Warmed Up Yet
That icy blast of cold air can stir up a sense of panic, particularly if temperatures are going to drop later in the day.
If this is the first time you’re turning on your furnace for the season, make sure to wait several minutes. It’s like bringing a kettle to boil – the heating process doesn’t happen instantly. Instead, your heating cycle needs time to get rolling before it starts blowing hot air.
After approximately 10-15 minutes, start moving down this list if the furnace heater blowing cold air continues.
2. Your Thermostat is Set Incorrectly
Thermostats make our lives so much easier. They’re also the first place you should look if your furnace heating cycle isn’t working properly or you feel cold air coming from your vents.
It’s easy to have your thermostat settings incorrect, particularly when the seasons change from summer to fall and we turn on our furnaces for the first time. If you can feel the furnace blowing cold air through the air vents, maybe you set it for the summer and never changed it when you put your air conditioning unit away for winter!
You want to make sure that your thermostat setting is ‘Auto,’ not ‘On’. When it’s set to ‘on’, the fan on your furnace will blow even when your furnace isn’t on. When it is set to ‘Auto’, your furnace and fan will come on at the same time, as intended.
There’s also a possibility your thermostat isn’t working properly.
3. The Furnace Filter is Dirty
Air filters catch dust and debris we generate in our homes—that means they need to be changed on a regular basis.
An overly clogged dirty filter will limit air flow to your furnace and could cause it to overheat and turn off. The heated air has nowhere to go, and then the furnace blowing cold air is all you’re going to get!
This is something you can check yourself – just make sure your furnace is turned off before you look at or remove the air filter from the air handler. Make sure the clogged filter is changed every 90 days. If you have forgotten about it, now is the time to get rid of that dirty air filter! Is your furnace making whistling noises? You probably have a dirty air filter.
Changing out your furnace filters is a really important, low-cost maintenance that can prevent your furnace’s heat exchanger from getting damaged, which is a very expensive furnace repair bill. If that happens, your furnace blowing cold air might be the least of your worries!
4. Your Furnace Has Overheated
When your furnace overheats, there’s a safety mechanism that actually will shut your furnace down. So not only will your furnace blow cold air temporarily, but it’ll actually shut off.
There are a few reasons your furnace could be overheating (besides a clogged air filter):
Dirt buildup – if your air filter was clogged, chances are dirt and debris worked their way into other parts of your furnace. If that dirt is in moving components, like the furnace blower fan, it can restrict air flow and cause your furnace to overheat.
Mechanical failure – as a furnace experiences wear and tear, it’s possible for your furnace to overheat because one of the moving parts isn’t performing correctly (or at all). This may be the source of why your furnace is blowing cold air, particularly if you have an older furnace.
Age – as a furnace ages, it stops performing as well. Furnaces usually last around 15 years. Even with the best preventative maintenance, it won’t last forever and could start overheating if certain parts can’t perform. Typically the furnace burner itself, the flame sensor, or the gas supply pipe are to blame.
5. The Condensate Line is Clogged
High-efficiency furnaces have condensate lines that move water away from the furnace. Condensate is a byproduct of the combustion process, and if the condensate line becomes clogged, it can trigger a safety mechanism that shuts down the furnace.
A clog in the condensate line will prevent your furnace pilot light from igniting. No ignition means only cool air coming through your vents. There could also be an issue with your condensate drain lines, but an HVAC technician will be able to tell you exactly what the problem is.
6. The Pilot Light Keeps Going Out
This is mainly for older furnaces. Many new models of furnaces have an electric pilot light that only turns on when needed – older ones will have a pilot light on continually from the gas line. If you are comfortable doing so, you can relight it by following the instruction kit that came with the furnace (always turn off the gas before doing so).
Pilot lights can be very dangerous to replace, especially on a gas furnace, so please be careful to read the booklet that came with your heating system. It may also be a faulty thermocouple (the flame sensor that controls the gas and ignition) which needs replacing. If you are concerned about handling anything on your own, give one of our HVAC technicians a call.
7. There’s A Problem With The Gas Supply
Gas furnaces need a steady and adequate supply of natural gas or propane to combust and generate heat. Problems with the gas supply can lead to incomplete combustion or prevent the furnace from igniting. If your pilot light is going out instantly or not lighting at all, it may be an issue with the gas supply. If this is the case, we have good news: Your furnace is designed to shut off if there is an issue with the gas supply.
Without enough gas supply, the furnace fan may blow room temperature air or even cold air, as the heating process fails to activate.
There might be an inadequate gas supply in your tank, but it might also be an issue with how the gas gets to your furnace. If your pilot light doesn’t light at all, it may also be the gas valve. This is not an issue that you can do on your own; you need to call a professional from an HVAC or gas company.
8. The Air Ducts Are Leaking
If you have holes, disconnections, or leaks in your air ducts, then all the hot air is escaping before making it through your vents. Leaks in the air ducts can allow warm air to escape before it reaches the intended living spaces. As a result, the furnace may appear to blow cold air even though it is generating heat.
Sometimes this can be due to age. Other times it can be due to a small animal biting or clawing at them. Leaking ducts have more of an effect than you’d think, and duct sealing would fix this problem—either with tape or new pieces depending on the damage. Have a professional do an inspection to find the problem areas.
9. The Coils are Clogged
The evaporator coil is a key component in the cooling process of an HVAC system. It is responsible for absorbing heat from the air, allowing the refrigerant to evaporate and cool the air before it is circulated throughout the home. If the coil becomes clogged with dirt, dust, or debris, it hampers the heat absorption process.
A clogged coil reduces the furnace’s ability to absorb heat efficiently, leading to your furnace blowing cold air instead of warm air. It may also cause the furnace to overheat, triggering safety mechanisms that can result in the furnace blowing cold air to prevent damage.
10. The Air Vents are Blocked
Adequate air flow is crucial for the proper functioning of a furnace. Blocked or closed air vents impede the furnace’s ability to draw in a sufficient amount of air needed for combustion and heating.
Limited airflow causes the furnace to work harder, potentially overheating the heat exchanger. When this happens, your furnace can start blowing cold air, and it can also lead to uneven heating in different areas of the house.
11. The Heat Exchanger is Cracked
The heat exchanger is a critical part of the gas furnace pilot light assembly that separates the combustion process from the air being circulated. If the heat exchanger develops cracks, combustion gases, including carbon monoxide, can mix with the circulating air.
A cracked heat exchanger can compromise the integrity of the heating system, leading to safety concerns and reduced heating efficiency. Your furnace blows cold air as a result of the compromised heat exchanger, and it poses serious health risks due to the potential release of harmful natural gas into the living space.
Have Husky Come Take a Look
It’s safe for homeowners to try fixing the thermostat and air conditioner. But if your furnace is still blowing cold air after you’ve tried those, call us to have an HVAC technician help you out – don’t try to repair your furnace yourself.
The friendly professionals at Husky can diagnose and repair the problem on any make or model of furnace. We can also perform preventative maintenance after the repair is complete to prevent your furnace blowing cold air from happening in the future.
FIX YOUR FURNACE THAT’S BLOWING COLD AIR