Brrr! Why does the furnace quit on the coldest day of the year and always on a weekend?
We feel your pain! So, to help, here are a few things you can do to troubleshoot the problem before you have to call for an emergency repair.
Top 3 Reasons a Furnace Blows Cold Air
#1 – Your Thermostat Is in the ON Position
Your thermostat has an ON and AUTO switch that runs your blower. If the switch is in the ON position, then the blower keeps running, even when the furnace is not heating. As soon as the furnace cycles back on the air will warm up again. All you have to do is switch the thermostat to the AUTO position. Then, the blower only comes on when the furnace heats.
#2 – The Pilot Light Is Out
A gas furnace has a small pilot light that stays on all the time. When the furnace cycles on, then the pilot light provides the flame that lights the gas and warms the air. If the pilot light goes out, then there is nothing to light the gas that fires the furnace. Lighting a pilot light is not hard but there are a few safety measures you need to follow.
Never try to light a pilot light if you smell gas in the room. Call your gas company’s emergency line and they will send someone to inspect your furnace lines.
If you don’t smell gas, then find the pilot light assembly. Most furnaces have a sticker with instructions on how to light the pilot light. If yours does not, then try to locate the gas valve. Switch it to the PILOT setting. Hold a lighted match to the pilot opening. If there is a reset button on the control panel, hold the button until the pilot light burns. Once it is going, set the valve to the ON position. If the pilot light won’t stay lit, then you may have a faulty thermocouple or a dirty port. You can try cleaning the port with a piece of wire. If the thermocouple is bad, you will need to call a professional to make the repair.
Some furnaces have an electric starter instead of a pilot light. If you cannot find a pilot light, then an electric heating element is probably what ignites your furnace. When an element malfunctions, you will need to call an HVAC professional.
#3 – The Furnace Has Overheated
If you can’t get your furnace to blow any air, hot or cold, it’s possible it has overheated. Safeguards are in place that shut off the burners when the unit gets too hot. More often than not, the problem is a dirty air filter. Furnace filters should be checked frequently for dirt and debris. If you have pets you may find that you have to change out your filter as often as once a month. Once the air flow is no longer restricted and the unit cools down, the furnace should start blowing warm air.