4 Reasons Your Furnace is Blowing Cold Air

senior adjusting temperatureThere are several possible reasons as to why your furnace is blowing cold air. The good news is you can easily fix most of the common ones yourself, before calling for furnace repair.

We’ll explore what those are and what you should do to fix them.

1) Thermostat is set to ON and not AUTO

Is your furnace blowing cold air sometimes? Is the furnace’s blower always running? Your thermostat is probably set to “ON”, meaning the furnace’ blower will keep blowing air regardless of whether it’s being heated or not. Turn it back to AUTO so the blower will only blow when the furnace is heating the air.

2) Pilot light out

If your furnace is blowing cold air – isn’t blowing any hot air at all, and your furnace is 24+ years old, then the pilot light may be out. The pilot light hits a thermocouple to keep the gas flowing. And when that thermocouple isn’t heated by the pilot light, it shuts a gas valve to the burners so the furnace can’t ignite.

Relight it by following these steps:

  • Step 1: Find the pilot light assembly and reset switch – The assembly and switch are usually located at the bottom of the furnace near a small knob that usually these 3 settings: “Pilot”, “Off”,  “On”.  Find your furnace user manual and there should be a diagram to show you where it is.
  • Step 2: Turn the knob to the “off” setting.  Wait 3-5 minutes to make sure no gas is coming out of the pilot.
  • Step 3: Turn the knob to the “pilot” setting and press down the knob for awhile. This re-starts the flow of gas to the pilot.
  • Step 4: Hold your lighter to the pilot opening until the flame lights. The flame should be a steady blue cone that hits right in the middle of the thermocouple.
  • Step 5: Turn the knob to the “on” setting.  The furnace should ignite and you should be getting hot air now.

If the pilot won’t light or it lights but won’t stay lit, then there are several possible problems (like a malfunctioning thermocouple) that require a professional technician.

Even if you fix this problem, you should consider getting a new furnace. Pilot light furnaces haven’t been made since 1992 and those furnaces have an average lifespan of 18-20 years.

3) Gas supply problems

If no gas is getting to the furnace, then the burners can’t light. If they can’t light, then the furnace can’t warm the air, which feels like the furnace is blowing cold air.

So you may want to check if:

  1. The furnace’s gas valve is closed. The furnace’s gas valve switch needs to be parallel/in line with the gas supply pipe. That’s the “on” position.
  2. Your gas supply company is having problems. Contact your gas supply company. They may be having issues you’re not aware of.

4) Broken furnace component

If you have determined that the thermostat, pilot light and natural gas supply are not the problem – then there is a likely a problem with your furnace. If this is the case call an expert furnace repair technician, like the ones at Airplus Heating and Cooling of Toronto and the GTA at 416.298.6974.  Airplus services Toronto, Markham, Richmond Hill, Pickering, Ajax and Oshawa, Mississauga, Oakville, Burlington and Milton and Brampton.


If you were not able to fix your problem, contact us for help.  AirPlus Heating & Cooling offers flat rate repair and 24 Hour service.  Our experienced, licensed technicians approach all jobs with safety as a priority. Call AirPlus Heating & Cooling at 416.298.6874. Airplus has an A+ rating with the Better Business Bureau.

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