[HayZee518]

for the sake of trying to find the problem, jumper out the switch that the vacuum line goes to. if you had a shematic of the furnace this would help considerably as I could see how its wired and aid in finding out the sequence of events when it was coming on. the flame sense is a flame rod unit. once a flame is established the gas/air between the flame rod and ground ionizes and conducts as if it were dc. this dc is fed to the electronics to establish a flame - no flame and locks out the burner.