Tube that runs through the bulkhead goes to a combination brake light switch/vent valve for the cruise which cancels the cruise when you touch the brakes. They do fail but are cheap to replace. The cruise pump is driven by a ecu and invertor ..looks like a red relay..both are located behind the dash, just below the instrument cluster. remove the drivers kick panel (One with the small vent by your knees)..4 blanking caps and screws underneath. The switch is operated directly by the brake pedal. Additionally, there is a comprehensive step by step fault finding procedure for the cruise control in the electrical secion of RAVE:behindsofa: