Calgary Plumber fixing a broken Furnace

Why Is My Furnace Blowing Cold Air?

A cold winter morning in Calgary is a bad time to have to deal with a furnace blowing cold air.

That just gets the day started on a real downer.

But don’t despair. There may be a simple reason for it. You may not have to call on life-saving furnace repair technicians just yet.

It helps to know what you can check yourself and what you need a professional for.

If you are familiar with the possible reasons that your furnace is blowing cold air, you can take a few simple diagnostic steps before picking up the phone …


Why is my furnace blowing cold air instead of heat?

There are more than 10 different reasons your furnace could be blowing cold air instead of hot air around your home.

These are the main ones to check…


An error in the thermostat fan settings is one of the most common – and easily fixed – problems with furnaces.

The fan setting on your thermostat has two options: ON and AUTO. If it is set to ON, the fan will run continuously even when the furnace is off. That can result in cold air blowing around the home.

No repairs are needed for this simple problem that can be caused by someone deliberately or accidentally flicking the fan switch to ON.

Simply change the thermostat to AUTO. Then it will only turn on when it detects that the home’s air temperature is different from the thermostat setting and warm air will circulate.

If that doesn’t work, and you’ve had your furnace a long time, the thermostat battery may need changing.


How to fix a furnace blowing cold air?

Most furnace repairs require a callout from a professional furnace technician - especially if you are not used to working with furnaces.

There’s no harm in going through the above checklist to diagnose the problem, and you might be able to manage a few simple “fixes” yourself. If in any doubt, call one of our professional technicians…

Pilot light out

If you have an older furnace with a continuous pilot light that has gone out, simply try to relight it. To do this safely, follow these steps:

  • Turn off the power
  • Locate the pilot light assembly and turn the reset switch to OFF
  • Wait 10-15 minutes to allow escaped gas to clear
  • Turn the reset switch to PILOT and light the gas using a match or lighter
  • Once the pilot is lit, turn the switch to ON
  • Switch the power back on

If that doesn’t work, call a repair professional.

Inadequate gas supply

Another easy fix to common furnace problems is to ensure that the gas supply to the system is sufficient. Some new homeowners not used to operating gas/furnaces get caught out by this problem.

Check for simple issues first. Is the gas supply turned to the ON position (parallel and in line with the gas supply pipe)?

Furnace air filter issues

Another simple fix for a furnace blowing cold air is to replace the air filters, which can become clogged and dirty, leading to overheating of the system. This should be done regularly as part of a maintenance check.

To do this yourself, follow these simple steps:

  • Remove the access door of the filter compartment on your furnace
  • Slide out the old filter
  • Insert a new filter, following the directional markings on the filter frame
  • Refit the access door to the compartment

Standing water around the unit

Standing water around an older furnace may be a sign that you should call a professional immediately.

However, it is likely nothing to panic about if you have a modern high-efficiency furnace. These produce condensation, which exits the system to the outside of your home through the condensate drain line as already explained.

A blockage to these lines may cause standing water to form around the unit and the system to shut off. You can clear condensate drain clogs by following these simple steps:

  • Turn off power at the breaker
  • Locate the condensate drain pan
  • Remove water from the pan using a wet/dry vacuum
  • Clean the pan with ordinary dish soap and reinsert it
  • Find where the condensate drain pipe below the pan exits your home
  • Attach your wet/dry vacuum to the end of it and suck out any clogs
  • Switch the power back on

If that fixes the problem, great! If not, it needs a professional.

Prevent furnace problems with regular maintenance

A little preventative maintenance can save money on expensive furnace repairs in the long run. Whatever type of furnace system you have installed, we will customize a maintenance plan that works for your budget.

Call Alpha Plumbing on 403-470-5785 to arrange an honest assessment from a qualified technician.

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