[Ascaris]

I wanted to add, if the switch is defective it could cause the light to be on all the time. If memory serves, the switch opens the circuit when the button is pressed by the parking brake handle (brake in the off position). If it has corroded or gunked up enough to short the switch, the light would stay on. Another possibility is that the little "leg" on your brake handle is bent or missing so it isn't pressing the button.