The joys of using cruise control........................ and then it fails
The system uses 3 primary components to engage cruise control.
1. The Vac pump unit attached to the EAS box.
2. Two electronic modules located on right side under lower dash trim.
Rarely do all three items go but it can and does happen, to date I've had to replace all three components on two Range Rovers P38's, the usual problem with a non functioning CC is cracked piping on the system.
This pipe runs from the Vacuum pipe to the brake pedal where it is attached via a vacuum breaker switch.
The pipe ends crack (due to age) on both ends, also note that on the Vacuum pump end the pipe is split into an additional two more shorter pipes, these two need inspecting, any sign of cracks in the piping requires replacement using a suitable thick walled rubber pipe, a good quality fuel hose usually works well.
Pictures of the Electronic modules to follow soon