Why is My Furnace Blowing Cold Air?

Furnace, HVAC News

When the cold wind starts to howl, you may hurry to your furnace … only to find that it’s blowing chilly air throughout your home. This can be aggravating, but there are a few ways to pinpoint why your heater is functioning more like an air conditioner.

Check Your Thermostat

The first thing to watch for when your furnace seems on the fritz is your thermostat. If you call a technician to the house, this is the first place they’ll look, so save yourself the trouble by eliminating this step. Is the thermostat set to “on” or “auto?” If it’s set to “on,” then the furnace will blow air continuously, whether it’s heated or not. If you change your settings to “auto,” your furnace will kick in only when the air drops below your set temperature, and that air should be warm.

Is Your Pilot Light Out?

If you have a gas furnace and your thermostat is set to “auto,” the next step is to check your pilot light. Just as your stove won’t light when the pilot is out, a furnace won’t blow hot air if the pilot light is out. If you check and find that it’s out, you have a few options:

Try relighting it. If it stays lit, then problem solved!

If it won’t relight, check to see if there is gas running through your line. Check to see that the gas is on the “on” position (the valve should be parallel to the gas line). Also, check to see if the pilot light area is dirty. If the valve is in the “on” position, clean the pilot light and try relighting it.

If your pilot light stays on just momentarily, you may have an issue with the thermocouple. It may need to be replaced or adjusted. In this case, it’s best to contact a professional.

Your Furnace Is Overheated

It sounds counterintuitive, but yes, your furnace can overheat. You may have this problem if your furnace starts to blow hot air, then switches to cold air, and then switches back to hot air again. Your furnace has built-in mechanisms that are designed to keep it from overheating to dangerous levels, which is why you’re feeling bouts of cold.

The most common cause of an overheated furnace is a dirty filter. You should replace your filters often (a few times a year), especially if you have pets. Try replacing the filter and see if the problem stops.

If it continues, do not ignore it. If your furnace continues to overheat, you could break the unit’s heat exchanger, which is an expensive fix.

These are some common reasons why your furnace could be blowing hot air, but it’s not an exhaustive list. If you’ve run through our checklist and find that you’re still having problems, then it’s time to call an expert at Patriot Air Comfort Systems. We’ve been helping customers repair and replace their furnace systems since 2004. Don’t delay in bringing in a specialist; the longer you wait to address the problem, the more costly the repair. If you have any questions, contact us today!

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