I f you can't troubleshoot it by looking at it then time to call the service guy and open your wallet, very rarely does one save money while trying to save money, it's a paradox and is woven throughout life.
It's not if your doing it right it's whether your doing the right thing that is important.
I imagine the actual model is G12Q3-82 if Lennox. Be careful messing with this furnace, if the burners DON'T ignite and the gas builds up, you've got an explosive situation on your hands. Call a professional right away as it could be VERY dangerous! This old a unit has very few safeties (sp?) compared to the newer units. Don't spend much on this unit as the efficiency is very low and it's old.
I can only remember seeing 1 duracurve that wasn't cracked. I was very surprised!
"Hey Lama, hey, how about a little something, you know, for the effort." And he says, "there won't be any money, but when you die, on your deathbed, you will receive total consciousness." So I got that goin' for me, which is nice. - Carl Spackler