M450 and M380 center brake lights
 

John, you should check the wiring to the lamp. I had one of the center brake lights malfunction on my M380. Once I pulled the lamp out, I found a broken wire. Seems on my coach, the heavy wiring bundle is suspended by the smallest, shortest, most fragile wire connecting it to the lamps. I repaired the broken wire and added a few tie wraps to prevent the bundle from dangling from the small wires and flailing around every time I stepped on the brake.

brake light lens
 

This picture is correct, I will check 12 or 24V. Lights are working, just a cracked lens.

John