Here's Why Your Heater Is Only Blowing Cool Air

When winter hits, the one thing you want to function perfectly is your furnace. If you're only feeling cool air coming from the vents, however, you may start to worry. There are several reasons your furnace can stop working, but many things you can do on your own to try to fix it before calling for help.

It Doesn't Have Power or Fuel

Whether your furnace uses electricity or gas, if it's not receiving the power or fuel it needs to run, then it won't be able to turn on even when you set your thermostat. There are a few different places this problem might be occurring.

If you have an electric furnace, first check your circuit breaker to see if anything has tripped. Because of the power necessary for a furnace, most furnaces will be installed on a dedicated circuit, which means that you might not notice its circuit has tripped until you try to turn it on. If you reset the switch and the furnace still won't turn on, check the furnace itself. Typically, there will be another switch on the furnace itself that allows you to turn power to the unit on or off. If the switch is off, turn it on and try again. If it keeps shutting off, call a technician before trying to use the furnace again, as you may have an electrical issue.

If you use a gas furnace, you'll still need to check the breaker, but your next step will be a little different. Check your gas supply line near the furnace itself and look for a valve on the gas supply line to make sure it's open. It may need to be twisted to be turned on, but if you see a handle, then it will need to be turned parallel to the supply line; if it's perpendicular, it's shut off. Make sure it's switched on, then try again.

Its Air Supply Is Blocked

Just like an air conditioner, your furnace needs to be able to take air in and push air out smoothly. If either the intake or outtake has too much resistance, the furnace may shut itself off automatically as a safety feature.

The first way this can happen is if the furnace filter hasn't been replaced recently. A dirty air filter makes it harder for the furnace to pull in air, which can cause the furnace to start to overheat. Rather than overheating and damaging itself, it will shut off. If the filter is very dirty, replace it before trying to use the furnace again.

A second problem is if the air registers are closed. Even if your furnace is pulling in air just fine, if it can't push it out into your home fast enough, the same overheating problem can occur. Check the registers in your home to make sure no more than a few of them at most are closed and make sure you can feel a steady supply of air from each.

Something Needs Resetting or Cleaning

Your furnace has several different settings, modes of operation, and safety features that help make sure it runs safely and smoothly whenever you turn it on. Sometimes, it may be necessary to reset your furnace or make sure some of its parts haven't become too dirty.

First, look for your furnace's fan limit switch. You may need to check your manual to see where this is located depending on what model you're using. Make sure it's set to "Auto" rather than simply to "On." Auto ensures that the furnace will only blow air when the furnace is heating, while an On setting means it will blow air regardless.

Second, if your furnace makes use of a pilot light and you see that the pilot light has gone out, light it again following the settings in your manual. If the pilot light keeps going out, there may be a gas-related issue, and you will need to call a technician for repairs.

Third, try cleaning the flame or ignition sensor. If this gets too dirty, it will not allow gas to flow, preventing your furnace from turning on. Be sure to turn off your gas supply before attempting this. If you don't feel comfortable trying this yourself, a technician can examine it for you.

Finally, if your furnace has a reset button or reset operation, try doing this. This can take the form of pressing and holding a reset button, or it might involve shutting off the gas supply, then turning it back on and re-lighting the furnace. This can solve many problems quickly and is worth a try.

For more information, contact a local heating repair service.