Originally Posted by dergish
It's on a Freightliner chassis, The brake light goes out, When you put it in gear, dinging starts,,, when you put it back into neutral, dinging quits.
With the park brake off, this is exactly the reverse of what should be happening. My guess is the brake sensor, located along the frame rail, driver side, just in front of rear axle.
I would verify this with the Freightliner help desk before buying parts, but mine would come on driving down the highway. Stopping, applying the park brake, then releasing the park brake would sometimes stop it for a while. Replacing that switch fixed it.