When your furnace stops turning on, blows cold air, or short cycles, our furnace guides help you diagnose the cause before you pay for a service call. Covering thermostats, ignition, flame sensors, error codes by brand, and honest repair costs — with clear guidance on when a problem needs a licensed HVAC pro.
Last updated: July 2026 · Reviewed against oil furnace service documentation Oil furnaces heat millions of homes, especially across the Northeast, and they work differently from gas furnaces — burning heating oil from a storage tank through a burner and nozzle. That means different maintenance, different problems, and a different repair approach. Whether yours won’t … Read more
Last updated: July 2026 · Based on Goodman service documentation and diagnostic codes Goodman furnaces are known for being affordable and widely serviceable — parts are common and most repairs are straightforward for any HVAC technician. Whether your Goodman is not igniting, short cycling, or flashing an error code, this guide covers the most common … Read more
Last updated: July 2026 · Based on 2026 US contractor pricing Furnace repair costs $150 to $650 for most common fixes, with the national average around $300. But the range runs from a $15 flame sensor you can clean yourself to a $2,000 heat exchanger that often means replacing the whole furnace. Knowing what each … Read more
Last updated: July 2026 · Reviewed against Carrier, Goodman and Trane operating instructions Most furnaces built in the last 25 years do not have a standing pilot light — they use an electronic igniter instead. If you have an older furnace with an actual pilot, or a gas wall/floor furnace, here is how to find … Read more
Last updated: July 2026 · Reviewed against Carrier, Goodman and Trane service documentation The furnace limit switch is a safety device that shuts off the burners if the furnace overheats — and when it fails or trips repeatedly, it is a common reason a furnace short cycles, blows cold air, or stops heating. The good … Read more
Last updated: July 2026 · Reviewed against Carrier, Goodman and Trane service documentation The flame sensor is behind more furnace no-heat calls than almost any other part — and cleaning it is often a free, five-minute fix. This thin metal rod confirms the burner has lit; when it gets coated in carbon, it can no … Read more
Last updated: July 2026 · Reviewed against Carrier, Goodman and Trane service documentation A furnace not blowing hot air — or no air at all — usually comes down to a thermostat setting, a dirty filter, a blower problem, or the burners failing to fire. Whether the problem is no air or cold air points … Read more
Last updated: July 2026 · Based on manufacturer lifespan data and HVAC industry averages A furnace lasts 15 to 20 years on average, though the real number depends heavily on the fuel type, how well it was maintained, and how hard it worked. A well-maintained gas furnace often reaches 20 years; a neglected one may … Read more
Last updated: July 2026 · Reviewed against Carrier, Goodman and Trane maintenance guidelines Regular furnace maintenance is the single best way to avoid a mid-winter breakdown, cut heating bills, and make your furnace last 15–20 years instead of 10. Most of it is simple enough to do yourself — changing filters, clearing vents, checking the … Read more
Last updated: July 2026 · Based on Lennox integrated control (board) diagnostic flash codes A blinking red light on a Lennox furnace is the control board telling you exactly what is wrong — in code. The blink pattern (slow flash, fast flash, or a number of flashes) maps to a specific fault, from a normal … Read more