850 T-5R L5-2.3L Turbo VIN 58 B5234T5 (1995)
Brake Switch (Cruise Control): Description and Operation
Vacuum valves (pedal valves)
These are identical. A spring-loaded piston actuates a micro switch and a vacuum valve. The valve is sell-adjusting as small plastic catches hook on to
the piston, holding it in place.
When adjusting, the pedal is pressed down so the piston can be removed. The pedal is then released carefully so as not to push the piston back too tar.
In the normal position, with the pedal up, the spring is compressed, the switch contacts are closed and the vacuum valve is closed.
When the pedal is pressed for braking or declutching, the spring forces the piston back.
This opens the switch contacts, so that the ground circuit of the control module terminal 9T opens and de-energises the relay. At the same time the
vacuum valve opens, admitting ambient air and disengaging the cruise control.
Brake light switch
The brake light switch acts as an extra safety feature if the brake pedal is pressed down but the vacuum valve does not open. The brake light switch
opens when the brake pedal is up and closes when the brake pedal is pressed down. Control module terminal 6T is grounded via the brake light bulbs
and the control module controls the negative pressure in the system. As the control module is grounded through the brake light bulbs, these must be in
working order for the cruise control system to operate. If the system develops a fault, the first thing to check is the brake light bulbs.
