My furnace comes on just fine. Runs for a little while and will raise the temp a degree or two then it shuts off but the blower still blows out cold air. Flame sensor had been replaced, air filter is replaced, pipes checked for condensation, chimney checked for blockages, thermostat replaced. If I turn off the furnace and turn it right back on it starts all over.

  • 5
    Most furnaces have an LED (sometimes behind a little window) that indicates fault codes. It will do a certain combination of short and long flashes, and there should be a label explaining what the codes mean. Can you see if yours is showing any error codes? Also, we would need to know the brand and model of your furnace to help more. Nov 2, 2021 at 13:19
  • Manufacturer/Model #? Nov 2, 2021 at 13:26
  • Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer.
    – Community Bot
    Nov 2, 2021 at 13:33

1 Answer 1


Had a similar problem with an old Lennox furnace, both LEDS showed OK. Turned out to be the controller board.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.