Why Is My Furnace Blowing Cold Air

Furnace Blowing Cold Air

If your furnace is blowing cold air, we’re sorry! It’s a chilly problem that no one should have to deal with during winter in the Philadelphia area!

There are several possible causes for a furnace blowing cold air, so it’s hard to give you advice without more information.

But here are 3 common causes you can fix yourself.

     1) Thermostat is set to Fan ON not Auto

Is your furnace blowing cold air only sometimes? Is the furnace’s blower constantly running?

Check your thermostat. (That’s where a tech will start first, so you should as well.) If      your thermostat’s fan           setting is set to ON, the furnace blower will constantly run even when your furnace isn’t heating the air.

  • Solution: Turn your thermostat’s fan setting to AUTO. Now your furnace will only blow warm air.

  2) Furnace overheated

Let’s say your furnace blows hot air, then cold air, but then stops blowing any air at all after a while. What’s the             problem?

  • It’s possible your furnace overheated. If so, the limit switch, a furnace safety device, turned the furnace burners off.  The blower keeps blowing to cool the furnace down to a safe level.
  • So what causes the furnace to overheat? Most commonly,a dirty furnace air filter.
  • The dirty air filter will block airflow, causing the furnace to run longer to heat your home until it overheats.
  • Solution: Change the air filter and see if your furnace starts only blowing warm air.
  • DON’T ignore this problem. Repeated overheating will hurt the furnace’s heat exchanger, which is expensive to fix.

  3) Pilot light is out


If your gas furnace is only blowing cold air, then the pilot light may be out. Check to see if it is and try these solutions:

Solution 1: Relight the furnace pilot light. If the flame stays on, great!

Solution 2: If the pilot refuses to light, ensure that gas is flowing into the furnace. Make sure the furnace’s gas valve switch is in the “on” position (parallel/in line with the gas supply pipe. if the switch is on, then check to see if the pilot light is dirty. if it is, clean it to allow gas to come through.

Solution 3: If the pilot lights, but won’t stay lit, then there’s a problem with the thermocouple (the copper rod you see the pilot flame hitting). It needs to be adjusted or replaced. If you don’t feel comfortable doing this, please contact a professional.

Still having problems? Ask one of our experts for help. Give us more details about your problem, and we’ll get back to you ASAP!

HVAC Philly Air Conditioning, Heating has been serving the Philadelphia Metro area for over 20 years. Contact us online for more information on how we can help you.



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