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Furnace Blowing Cold Instead of Hot

The one thing you want in your life that is full of hot air is your furnace. And when it will only blow cold air, it is infuriating along with being uncomfortable. So why is your furnace blowing cold air? Don’t worry it isn’t personal and you are in the right place because we have compiled a list of potential reasons for you. 

Thermostat

Check to make sure your thermostat is properly set and somebody hasn’t changed the settings on you. 

Fan limit switch

There are two reasons your fan limit switch could be making your furnace blow cold air:

1. it has malfunctioned; or

2. it is set to ON instead of AUTO. The result, your furnace blowing air all the time, even when it isn’t actively heating.

Ducts

Your beautiful hot air is leaking out your ducts and not making it into your rooms. Have a professional in to inspect and repair them where needed.

Pilot Light

Your pilot light is out, meaning it can’t ignite the fuel to heat the air. Relight your pilot light.

Thermocouple

If your pilot light keeps going out it could be your thermocouple. It’s job is to determine if your pilot light is lit. If it senses the pilot light is out, it shuts down the fuel supply to your furnace. If you have a faulty thermocouple, it won’t allow fuel into your furnace, then your pilot light won’t light and your furnace can’t heat the air, and you end up with a furnace blowing cold air.

Dirty Furnace Parts

Several parts will not work properly if they are dirty and coated in grime and can result in your furnace giving you the cold shoulder.

• Dirty and clogged air filters won’t allow enough air flow causing your furnace to overheat and shut down (a safety feature). 

• A dirty or worn out flame sensor can cause your burner to shut off. 

• Grimy valves and burners won’t work properly.

Regular cleaning and maintenance will help keep your furnace in tip top shape.

Control Panel

Some newer furnaces have computerized control panels and you may need to reset the panel (same as rebooting your computer).

Valves

You could have a faulty valve or a valve not working properly because it is stuck due to dirt and grime.

Vents

Too many cold supply vents were closed or are blocked causing the furnace to overheat and shut down.

Fuel Supply

A problem with the fuel supply can make your furnace circulate cold air.

On a cold Red Deer day, you really want your furnace to be blowing hot air. And for your furnace to work, all its components must work properly. If a component is having a problem, your entire furnace is having a problem. Some of these problems are easy to check and fix yourself. Others will require a professional. But the key to keeping your furnace happy and blowing hot air is regular cleaning and maintenance.