QuestionI have a '96 Disco in great shape. My only problem is that there is no sign of life with the cruise control. I have checked the vacuum lines under the hood. I found one bad, and replaced it. There isn't a lot of suction, but some. (I'm not sure how much there should be.) I am assuming that there is some electrical component in the switch? No light comes on when I press "SET". Actually, nothing happens when I press any of the cruise control buttons. Where do I start?
Thanks,
Donnie
AnswerHi Donnie,
finding the fault for disabled cruise control (CC) is often a matter of elimination. For the cruise to work, you have to be travelling over 45 km/h (28 mph). The fact that your CC switch does not light up could be either no power to the switch (check fuse 18) or the bulb is burnt out.
You found one vacuum leak and repaired it, that's good! However, a low vacuum is not NOT good. You will have test the CC vacuum pump to ensure it is getting the required voltage and that it is indeed working. There's also a CC electronic control unit (ECU) that governs all the components involved. If this is faulty, nothing will work.
There are set procedures performed by LR mechanics to isolate the many causes of disabled CC units. They are well equiped at finding the fault quickly and have the experience and tools to speed this process along. My first suggestion is to have the LR mechanics fix it.
If you have the time and tools to do this work then you must be aware that there are risks involved and you may end up towing your Disco to the dealership (ouch).
You may want to check to see if your brake vacuum hoses are not kinked or leaking. This is common cause for vacuum loss. It is also possible that the brake switch or brake switch vent valve is faulty. It could be the CC lockout relay that has failed. The list is long.
If you are determined to check this yourself, here's where I'd start:
1. Cruise control unit Under LH dash
2. Engagement (on/off) switch Dash panel
3. Cruise control switch Steering wheel
4. Rotary coupler Steering wheel
5. Vacuum pump Box under jack area in engine compartment
6. Brake/vent switch Brake pedal
7. Vehicle speed sensor Transfer box behind transmission brake
8. Neutral lock-out relay Behind RH lower 'A' post trim casing
9. Actuator RH engine compartment
These are the main areas of concern. After testing each of these components and you still don't have CC working, you'll have to perform continuity and voltage tests on all the corresponding wires, fuses and relays.
Best of luck and I hope this helps,
JohnMc
