- To replace or repair your thermocouple on a furnace the average cost is $100–$250
- A thermocouple is essential on older model furnaces that have pilot lights- it depends on a thermocouple to turn off its gas valve if the flame goes out
- Furnace thermocouples generally last up to 10 years if you keep it maintained (learn how to clean a thermocouple) and it was installed correctly- furnaces themselves can last 15-20 years
- To figure out if your thermocouple has gone bad or is broken, if the flame lights and then goes out when you let go of the gas control knob after holding on to it in for 20 to 30 seconds, that’s the sign of a malfunctioning thermocouple