If the furnace blower runs nonstop, check the thermostat fan setting first. Then overheating, a stuck fan relay, a wiring short or a fan limit switch set to manual. How to find which one.
A failing inducer motor stops a gas furnace from lighting at all. The signs, how to tell it from a pressure switch or venting problem, error codes by brand and what repair costs.
A tripping high limit switch shuts off the burners while the blower keeps running, so you get cold air. It is almost always an airflow problem. Causes, error codes and fixes.
Inducer runs but the furnace never lights? The pressure switch is usually telling you the vent, drain or hose is blocked. Error codes by brand, causes and what you can safely check.
Furnace booming when it starts? Learn why delayed ignition happens, how it differs from noisy ductwork, and when it is a safety issue.
Most gas furnaces last 15 to 20 years. Learn what affects furnace lifespan, how to find your furnace’s age and 9 signs it’s time to replace it.
Furnace turning on and off every few minutes? Learn what normal cycling looks like and 9 causes of short cycling, from dirty filters to oversized furnaces.
Furnace lights then shuts off after a few seconds? Learn how to clean a furnace flame sensor safely in about 15 minutes, and what to do if cleaning doesn’t fix it.
Furnace ignitor not glowing? Learn how to tell a bad igniter from a pressure switch or board problem, how it’s tested, and what replacement costs.
Furnace blowing cold air? Check the thermostat fan setting first, then work through 8 causes from a dirty filter and flame sensor to ignition and gas problems.