A furnace that won’t start can be stressful — especially on a cold day. But in many cases, the cause is something simple that you can check yourself before needing help. Below are six (easy-to-follow) steps to try first.
Safety Reminder: If you smell oil or gas, DO NOT attempt to restart the furnace. Turn it off immediately and contact a certified HVAC technician.
Make sure your thermostat is set above the current room temperature.
If your thermostat uses batteries, check and replace them if needed. A low battery can prevent the thermostat from sending the signal to your furnace, even if the screen is still lit. Try installing fresh batteries to be sure.
Why this matters: The thermostat signals the furnace to turn on. If it’s set too low—or if the batteries are dead—the furnace will stay off.
Locate the power switch near your furnace and make sure it’s in the ON position.
Open your home’s electrical panel (breaker box or fuse box) and check for the following:
Reset any tripped breakers or replace fuses with ones of the correct amperage (as labeled).
Look for the reset button on your furnace, oil burner, or chimney pipe. Press it ONLY ONCE.
What it does: The reset button restarts the burner’s ignition system. If it doesn’t start after one press, don’t press it again—this could flood the system with fuel.
If you hear a humming sound but the burner hasn’t started, look for the overload button on the motor (usually a red or black button) and press it.
What it is: This motor powers the oil burner. If it overheats or gets stuck, it will shut off until manually reset.
Look at the gauge on your oil tank. If it shows the tank is nearly empty (especially below 1/4 full), it may need to be refilled.
Why this matters: Low or empty oil is one of the most common causes of furnace failure.
Still Not Working?
If you’ve tried all of the above and your furnace still won’t start, it’s time to call a professional.