Are you talking about your Low Air warning Light? or your Park Brake Light?
The low air warning light works. It lights up when I have liw air pressure. Now with the maxi / park brake on and low air there is no buzzer sounding, which is how it should work. Let the park brake off with low air and the buzzer should buzz. However my buzzer does not buzz.
There must be a switch in the park air circut that will allow the buzzer to sound if there is low air and the park brake is off.
There is a park brake on warning light that works. But only supplies current to the light when park brake is on, not off.