All of the replies are correct,but I would go with the assumption of a bad ground first. It is easy enough to verify. As previously stated, it is forming a ground at the glowing light. With the power on, simply start activating the other circuits.
When you hit the right one, the lamp will go out, as well as the at fault lamp circuit.
If that is not the case, then you'll have to start looking at relays and such.
While probably not related, the larger red wires going into the start relay under the tank on left side, should be cleaned up, anytime you have the tank off. They are notorious for causing all sorts of difficult to trace maladies.
Airheads really are pretty simple to work on, compared to almost anything built in the last twenty years or so.
Just my 2¢.
I didn't use the cocaine to get high, I just like the way it smells.