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.