Troubleshooting A Furnace Blowing Cold Air
The sole function of your central furnace is to provide warm air and heating to the rest of your home, but a number of different problems and malfunctions can cause your furnace to start moving cold air. Thankfully, you can easily troubleshoot a furnace that no longer provides adequate heating to your home in order to maintain your comfort levels during the winter months.
Check the Thermostat
Though it may seem obvious, the most common reason for a furnace to be blowing cold air throughout your home is that the furnace actually isn't on, but your air conditioner is. This is usually just a matter of flipping one switch or toggling one setting on your thermostat, which is why so many people can simply forget about it, but if you notice cold air blowing through your ventilation system, double check the thermostat to ensure that your furnace is supposed to be on and the temperature is set at an appropriate level.
Overheating Furnace
The next leading cause of a furnace that is blowing cold air is if the furnace itself has overheated. If this occurs, your furnace will automatically turn itself of (a safety feature designed to reduce the risk of fire and the wear and tear that your furnace experiences). Furnace overheating can happen due to damage to the actual furnace that results in the improper functioning of your furnace, but more commonly it can be attributed to the fact that your furnace's air filter has become clogged with dust and other debris. This will limit the air flow to your furnace, causing it to work harder and thus overheat, automatically shutting itself off. Simply check your air filter by removing it from the casing in the furnace (usually you can do this by hand, but some models require a screwdriver, so check your owner's manual) and cleaning out any accumulated material that may be blocking air flow.
Extinguished Pilot Light
The final leading cause of a furnace that no longer properly heats your home is if the pilot light has been extinguished. This only applies to older gas furnaces: newer gas furnaces, electric and wood heat stoves won't have this problem, so the issue probably lies elsewhere. While you can try to relight a pilot light yourself, it does represent a safety risk, and a pilot light that has gone out sometimes points to more serious issues within your furnace itself. If you check your furnace and notice that the pilot light is out, it's a good idea to contact a heating repair professional to take a look at your unit to diagnose the problem.
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