I guess I wasn't clear. I do not have an "owner's manual". I never
got one. I do not know who installed the furnace.

Even if I did have an owner's manual, I doubt the information I am
seeking would be in there.

For example: If the ignitor is burnt out (open circuit), does the
control detect this and refuse to open the gas valve? Or... does it
open the gas valve, and then detect no flame, and turn the valve back
off?

Stuff like that.

EJ