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The last thing you want on a cold winter day is a furnace that only blows cold air. While there are many possible reasons for the malfunction, several causes are particularly common. Here are five problems to look for and what to do for each.

Why Is the Furnace Blowing Cold Air?

Thermostat

furnaceFirst, check if your thermostat is set to on or auto. Auto is the better choice because the fan will only turn on when the furnace is heating the air. If your thermostat is set to “on,” the fan will continue to run even when the furnace is shut off, blowing cold air into your home.

Overheating

If your furnace has overheated, a safety switch built inside may have turned the burners off to prevent damage. The blower will still push air out, but without the burners, the air will be cool. Usually, overheating occurs when the air filter is dirty and blocking airflow. Sometimes the filter is the wrong size or isn’t installed correctly. If changing the filter doesn’t help, call your HVAC service expert.

Pilot Light

If you have a gas furnace, the pilot may simply be out. Try relighting the pilot light. When the flame holds, you should be good to go. If the light won’t stay lit, check that the gas valve is on and that fuel is flowing over a clean area, as dirt can cause blockages. When nothing fixes it, the problem may be the copper rod hitting the flame called the thermocouple, which will need adjustment or replacement.

Leaky Air Ducts

Cold air from outside may be entering your ductwork through attics and crawlspaces, which then reduces the temperature of the air flowing from the furnace and into your home. Duct sealing is your best option to correct leaks.

Inadequate Gas Flow

If your gas valve is set to “on,” but there doesn’t seem to be enough energy flowing, check with the gas company for any issues. If their supply is in order, it may be the line to your home, causing your furnace to shut down as a safety precaution. Call your gas company for assistance.

 

Since 1957, the family-owned Biggerstaff Plumbing Heating & Air has been the reliable HVAC service team and plumbing contractor for the Lincoln, NE, area. Their staff can help you with any plumbing repair, furnace maintenance, AC repair, and water heater service. Visit their website for a complete list of offerings or give them a call at (402) 466-8118 for a free estimate or for emergency services.

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