I have a Lennox furnace which is about 14 years old, it has worked flawlessly until a few days ago. There have been multiple issues which have had myself and a friend of mine perplexed:
At that point I heard a clunking sound coming from my furnace, which I was able to find was the gas valve. If the gas valve were unplugged, a clicking could be heard from the board.
After resetting the board, the issue starts again.
Another issue which has come up is the fan to blow away obstructions (attached to pressure switch) will go on, blow, shut with diagnostic showing an obstruction, and then start again.
I have also had the issue where the gas will light for a few seconds, then go out. It cycled through until the fifth time when it finally stayed on.
AS of now, it is working fine, although it could start having problems again soon. I believe the problem to be the control board but want to get another opinion before buying one.
If I could clarify anything, please let me know.