15961566 - Switch Asm - Park Brake Pump ( AKA Rotten Green Switch or RGS)

Usually the pressure  switch fails by leaking all the fluid out or cycling the pump/ and or turning the warning light on , what year is your chassis ? , the earlier models have a switch at the base of the steering column than can fail and cause issues with reverse .

The brake will default to the applied position if switch fails. This in turn will burn the brake up and then cause the coach not to hold. You would want to replace the factory switches with our high quality set, part # US21 for starters. You will need to replace the brake shoes at minimum but may need other parts depending on severity of damage.