If your furnace is running, but it's blowing cool air, there are a few things you can check before you call an HVAC contractor for repairs. One thing you know is okay is the power supply, otherwise the furnace would not be blowing. However, if you have a gas or oil furnace, you'll also want to make sure the pilot light is lit and you have plenty of fuel. Here are some other things to check.
Don't forget to check your thermostat. One of your kids may have played with it or you may have it set wrong. The batteries could also be low, and this can affect how the thermostat operates. The thermostat should be set higher than the temperature in your home for the heater to kick on. Also, make sure the thermostat is on the heat setting and not flipped to the on position. When the blower is in the on position, it runs continuously and will blow cool air when the heater kicks off.
When it is set in the heat mode, the blower only turns on when the heater kicks on. Keep in mind, if you adjust your thermostat, you should allow several minutes of furnace operation before you decide something is wrong. Your furnace needs to heat the air and send it through the ducts and circulate throughout the system before you will feel warm air coming out the vents, and that could take several minutes.
Change The Filter
If the filter is clogged up, the airflow through your system may be decreased. However, sometimes, the airflow doesn't decrease much. Instead, your furnace works harder to suck in air from around the clog. This causes stress on your furnace and it may eventually shut down the heating element to keep it from overheating. By replacing the filter, and resetting the furnace, you may get the heat working again. Since a clogged filter can damage your system, be sure to change the filter on a regular schedule so it doesn't get clogged again.
Check The Ducts
A damaged duct can affect the airflow from your furnace. If the duct has a big tear in it or if a panel comes loose, air can escape into the attic and never make it out of the heating vent. However, if the damage is smaller, air will continue to blow out the vents, but cold attic air will get inside the duct too and mix with the warm air. The result is cool air blowing out the heating vents.
You may be able to fix a damaged duct yourself with duct tape, although it may be a temporary fix. If the duct was damaged by rodents, they may need to be cleaned or replaced. If your ducts are old and worn out, have a contractor take a look and see if you need new ducts installed.
If these simple fixes do not work, then you'll need to call a contractor, like WM Jean Electric Co, to make repairs on your furnace. The problem could be a blocked condensation line or worn electrical parts. To fully assess the situation, the contractor needs to remove the inner panel on your HVAC system. Once that's done, he or she can check for worn parts and test the electrical system. These internal repairs should only be done by a contractor for safety reasons and to protect the warranty on your furnace.