4 Things to Check When Your Furnace Won't Turn On

Many people get in the habit of only adjusting the temperature on their thermostat without touching any other settings. However, the change from the cooling to the heating season can easily throw you off if you aren't careful. Be sure that the thermostat is set to heat rather than cool so that the thermostat can send the signal to your furnace to start up.

When you inspect your thermostat, you should also take a look at the fan setting. It should be set to auto when you use your furnace, but you can switch it to the on setting as a test. This should cause your furnace blower to start running even if the furnace isn't heating, which will help you pinpoint whether you have a problem with the burners or ignition, or a more general problem.

Furnaces are high-powered appliances — so much so that your HVAC system accounts for a bigger power draw than anything else in your home. If your furnace won't come on, it may have simply tripped a breaker. This is particularly important to check if your furnace stopped working recently after you plugged another device or appliance into the same circuit.

In addition to the breaker in the main electrical panel, many furnaces have a dedicated shutoff switch. This switch is usually on the furnace housing or on a wall near the furnace so that a technician can shut off the power conveniently and work on the furnace safely. Make sure that both the main breaker and the shutoff switch are set to the on position.

The evaporator coils in a central air conditioner are responsible for cooling the air directly, and they are usually right above the furnace. As air passes over the coils, moisture in the air condenses on them and drains into a pan below. Humidity in the air can cause condensation to build up in the drain pan even when your air conditioner is not being used.

Many HVAC systems have a condensate drain pan with a float switch that shuts the system off when the pan gets full. This is to prevent water from spilling over the side of the pan and causing water damage in your home. The pan can become full and activate the float switch if a clog is in the drain line. Empty the pan and test your furnace again, and try using a stiff brush or diluted bleach to unclog the drain.

Just as a lack of power will prevent your furnace from starting up, so will an interruption in the fuel supply. If you have a gas furnace, you can quickly test whether you are getting gas from your supply line by testing another gas-burning appliance in your home.

Oil furnaces are somewhat more complicated to test for fuel problems, as you must check the level in your oil storage tank. Some tanks have a gauge on the side for convenience, while others need manual testing with a dipstick. Your fuel oil provider can give you specific instructions for checking your oil level at home.

These tips will help you respond effectively when your furnace won't start and may get your home feeling warm and comfortable again in no time. For more HVAC tips and quality service and repairs, count on us at Comfort Technology Heating & Air Conditioning.