Hello -

I have a carrier furnace (guessing 5-7 years old) that often doesn't start the 1st try. I hear the combustion fan come on, then the electric ignitor glows bright red, I hear a click and the burners kick on. Sometimes it works beautifully, other times it seems to sputter a few times then the flames stop. The house fan kicks on for 90 seconds then the cycle begins again - from what I've seen it always starts the 2nd time.

After this point, the light blinks 3-4 which indicates a flame sensing problem. Apparently this can mean many things, but most commonly it means the flame sensor is dirty. I have removed this sensor 3 times and scrubbed down with sand paper, hasn't seemed to make much of a difference.

To make trouble shooting this easier, I have captures 3 videos:

Video 1: Successful start - furnace Starts Fine. Cover is off so its easy to see the flames. Make sure to have your sound on!
http://www.youtube.com/watch?v=E2vk2OFzltM

Video 2: Semi Successful Start - furnace Starts after a brief stutter. Cover is off so its easy to see the flames. Make sure to have your sound on!
http://www.youtube.com/watch?v=tBuy96l_ryc

Video 3: Failed start - furnace fails to start. Cover is on - for some reason I am yet to get it to fail with the cover off. Make sure to have your sound on!
http://www.youtube.com/watch?v=iZ-wZPHZbtQ


Any thoughts?? Should I be worried? Is it time to get someone out here to look at this (and if so any idea what they might be replacing so I don't get totally screwed and let them replace the whole thing - and can anyone even give a ballpark figure on what a repair trip might cost) - or is there something I should be checking myself?


Thanks!

Put a meter on the gas valve wires and check to see if you have a steady 24 volts while the burner is starting and during the run. Intermittent problems are the worst to find. Also check and clean the sensor if this unit has one.