I have a 5 year old Broan furnace model M7RL 072A AW downflow condensing gas furnace. Here's the furnace startup sequence:

  • pump runs
  • ignitor glows
  • hear the click of the gas valve opening
  • fires up
  • runs 4 seconds
  • shuts down

The next 2-3 attempts it starts and runs fine, then it does it again. It never shows any codes. I have replaced the flame sensor , but still does it.

  • Hello, and welcome to Home Improvement. Might there be a draft problem? And, you should probably take our tour so you'll know how best to participate here. – Daniel Griscom Dec 29 '19 at 2:28
  • I have a different furnace that did the same thing. It turned out the the flue draft sensor relay was bad. The draft fan worked, the sensor worked, but the relay was bad. I had to replace the control board. I'm only leaving this as a comment because the board is expensive and needed much more testing than what you've done to isolate it, just giving a possibility to check. – Eric Simpson Dec 29 '19 at 11:51

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