Is Your Furnace Blowing Cold Air? These Could be The Reasons

Is your furnace not blowing cold air? Find out the possible reasons, also get HVAC service for residential air conditioning with Sandium. Don't suffer and book us now!

Updated on Oct 23, 2023
5 min read
Is Your Furnace Blowing Cold Air? These Could be The Reasons

Just like your air conditioner is a necessity in places with high summer temperatures, a furnace is required to keep you comfortable in the cold months of winter and it does get cold in NorCal in the winter.

A warm indoor temperature is comfortable and also keeps your house and belongings in a good state (especially avoiding frozen pipes).

But if there is any malfunction in your furnace, it will not be able to do its job, and you will notice the furnace blowing out cold air instead of warm. This is going to be really uncomfortable and become an emergency repair especially in the middle of winters.

In order to get your furnace fixed and blowing warm air again, it is important that you first understand the causes of cold air blowing out. Often the problem can easily be fixed at home, without having to call any HVAC technicians. 

Take a look at the following list that states some reasons for furnaces blowing out cold air instead of warm.

1. Wrong thermostat settings

This is the most common cause of receiving cold air instead of warm, and often goes unnoticed. You need to keep your thermostat set on AUTO. If this has been switched to ON by someone else in the house, the fan keeps running without providing any heat. Switching the setting back to AUTO will give you hot air again.

2. Incompatible thermostat

If you have chosen the wrong thermostat and installed it yourself, you will face issues because most likely the thermostat is not compatible with your HVAC system.

In that case, or if your thermostat is old and the battery is running low, you will not get hot air. To rectify the problem, either have a technician check your thermostat and system compatibility or change the batteries.

3. Oil furnaces

Just like low battery issues for electric furnaces, running out of fuel for oil furnaces will lead to lack of hot air. Make sure there is fuel, put more fuel in if there is not, and you are good to go. Otherwise the burners will fail to light up and hence not produce heat.

4. Technical glitch

Sometimes just restarting your system could help solve the problem. Switch off the system, wait for a few minutes, and then switch it back on. This is akin to rebooting a computer to get rid of a minor snag. If you still do not receive hot air, call an HVAC technician.

5. Extinguished pilot light

Older furnaces make use of a pilot light that is continuously on. This may go off at times due to a draft or if someone has been working near the furnace. Relight the pilot light to recommence heating. If you do not know how to do this yourself, get a technician to relight it for you.

6. Clogged air filter

If you have been using your furnace for a long time without maintenance, you probably have a clogged filter. This hampers air flow and causes the furnace to overheat. An overheated furnace will shut down the burner and give you cold air. Change the air filter and restart the furnace.

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