Top 5 Furnace Problems & Solutions: 2025

Having trouble with your furnace? You’re not alone. Fortunately, many problems have easy DIY fixes. The first step: Check whether your HVAC system has power. You don't want to have a service tech come to your home just to flip a switch at the breaker box. If power isn't the problem, check other possible glitches before calling for service.

Troubleshoot furnace issues with these tips from Martin Orozco, an HVAC pro at Sears Home Services. While these suggestions work for most furnaces, you should check your furnace's manual first to make sure you’re not voiding your warranty.

#1 PROBLEM: Thermostat Isn’t Working

LIKELY CULPRIT: If your heat isn’t coming on at all, try changing the batteries in the thermostat, if it has batteries. While you’re at it, give the thermostat a good dusting inside with a small paintbrush.

You can also try to reboot it. With the thermostat set to Heat, turn the temperature down to about 60º. Then, turn the breaker switch off for 30 seconds and turn it back on. Still nothing? Call in an expert.

#2 PROBLEM: Unit Not Turning On

LIKELY CULPRIT: Check the emergency shutoff switch for the furnace. It might be at the entrance to the furnace closet, at the top of the basement stairs, or on the furnace. It might have a red switch plate. If someone switched it off, the furnace won't work.

#3 PROBLEM: Dirty Filter

LIKELY CULPRIT: Not swapping out an old filter can cause a host of problems, not to mention driving up your energy bill. To ensure your furnace doesn’t work overtime, change your filter every one to two months. Here’s how:

1. Buy the replacement filter that fits your furnace.
2. Turn off your furnace.
3. Remove the old filter and replace it with the new one.
4. Turn the furnace back on.

#4 PROBLEM: Furnace Isn’t Igniting

LIKELY CULPRIT: Does your furnace click as though it’s about to turn on, but then go silent and never start? If you’ve checked the power, inspected the thermostat and changed the filter, the pilot light or the ignition sensor is likely the problem. To fix it, start by turning off the gas to your furnace. Then remove the front panel and find the igniter or ignition sensor, which is usually near the burners. Snap a photo of the sensor to remind you of how it's attached and then remove the ignition sensor. Rub it with steel wool to remove residue, being careful to not damage it. Then put it back exactly as you found it and replace the panel before turning the gas back on. If you have any hesitation about this project, play it safe and call in the pros.

#5 PROBLEM: Furnace Keeps Tripping the Breaker

LIKELY CULPRIT: If your furnace keeps tripping the breaker or blowing the fuse when the heat kicks in, it’s most likely an electrical issue. To keep you and your family safe, call in the pros to diagnose the cause.

Qualified Sears Home Services HVAC technicians can diagnose and rectify more complex gas furnace problems, ensuring your furnace works safely and efficiently.

Remember, a well-maintained furnace not only ensures a cozy home but also enhances the system's lifespan and efficiency. Regular maintenance and prompt troubleshooting can keep most of these issues at bay. We're committed to helping you keep your home warm and comfortable throughout 2024 and beyond.