Why Your Furnace Is Blowing Out Cold Air

Cold man in beautiful grey turtleneck blowing his cold hands in Boston, MA.
A furnace generates heat. That’s the basic job from when the first central heating furnaces were created hundreds of years ago. So when you turn on your furnace to provide your house with heat during a cold winter and the only air that comes out is cold—yes, you have a problem. There may be a simple solution to this, and we’ll look into that. Or you could have a serious problem that will require furnace repair in Andover, MA from professionals. We’re going to go through some of the basic reasons for a furnace that isn’t heating and what you can do about them. Please, if in doubt, do not attempt to make any repairs on your own. Especially with a gas furnace, trying to open up the unit and “fixing” it is potentially dangerous. (And you probably wouldn’t be able to fix the problem anyway.)

Thermostat issues

The first thing to check in a situation where the furnace isn’t doing what it should is to see if the thermostat settings are correct. Changing between seasons often means older settings are still programmed into the thermostat and interfering with your plans to heat your house. Also check to see that the setting for the fan is AUTO. The thermostat may be broken, in which case it either needs to be recalibrated or replaced.

Clogged air filter

The second place to look when trying to determine a simple cause for a furnace sending out cold air is the filter on the HVAC system. If it’s clogged up because it hasn’t been changed regularly, it will prevent sufficient air from entering the furnace to be warmed up. Replace the clogged filter with a clean one and see if this fixes the issue.

Failed ignition system

Or, a failed pilot light (if you have an older furnace). The electronic ignition system creates the sparks to light the burners. The ignition system usually has a shorter lifespan than the furnace itself and will probably need to be replaced eventually. Let an HVAC technician handle doing this job.

Faulty flame sensor

A flame sensor is a safety device that shuts off the gas flow to the burners if the burners fail to light. If the flame sensor malfunctions, it will turn off the gas while the burners are still running and won’t allow them to turn back on again. A technician can replace the old flame sensor with a new one to fix this problem.

Dirt and grime along the burners

The burners may be failing to light because they’re covered with dirt and grime, blocking them from the air they need for combustion. To clean the burners requires technicians remove the burner assembly, so don’t attempt to “clean” the burner on your own.

Broken gas valve

The gas valve that controls when gas flows to the furnace may be stuck shut. You can turn the valve to see if it was simply closed. If it’s jammed, don’t force it. Have a certified professional look over the gas lines and see what needs to be repaired.

Basnett Plumbing, Heating & AC has been trusted for over 30 years. Schedule service with us when your heating isn’t working.

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