How to Fix Inoperative Cruise Control on Series III XJ6 Jaguars
Jaguar Parts Technical Information
The cruise control system in these cars has a few common problem areas
which will render the system inoperative. Fortunately, they are easy and
inexpensive to repair. If your cruise control doesn't work, check the following:
- 1. Make sure the rubber bellows of the vacuum unit isn't cracked or split. If it's OK, then make sure it seals around the metal endplates. Use silicone sealant to really seal it up.
- 2. Check the disconnect switch at the brake pedal. The wires may have broken or become disconnected. This is the switch that deactivates the cruise control when the brake is pressed.
- 3. Check that the vacuum supply hose to the bellows unit is intact, and is plugged into the intake manifold.
- 4. The "set switch" at the end of the turn signal stalk sometimes loses its electrical ground. You can restore the electrical ground by removing the bottom of the steering column just behind the steering wheel, and wrapping a small piece of wire around the turn signal stalk. Connect the other end of the wire to a suitable grounded screw. Replace the lower column cover and your repair is invisible.
- 5. The solenoids at the end of the bellows unit sometimes stick. Remove the black caps and spray penetrating oil into the solenoids. Allow the oil to sit and work for a while before attempting to use the cruise control. If you've taken these steps and your cruise control still doesn't work, then you're probably looking at something expensive.
Forest Gibson, one of our list members, added:
Jose Maymon, another list member, added:
Jose Maymon added another update: 06/20/2004:
"Regarding the posting I made years ago to your Series 3 XJ-6 Technical Tip maybe the following correction should be added: It appears that the microswitch in question has nothing to do with the Reverse Lights in my 1984 XJ-6 as I stated in that posting; I am referring to the Start Inhibitor/Cruise Control micro-switch located in front of the Gear Lever Quadrant, under the center console 'Ski Slope panel' (where the ashtrays mount to)."
"Yesterday I was adjusting my Gear Selector Cable, in order to locate the 'sweet spot' adjustment for the Reverse Lights to come on, because they were not coming on when the Gear Selector was moved to 'R' unless I pushed the Selector slighty forward. I removed the Start Inhibitor / Cruise Control micro-switch from its mounting and disconnected it from its Harness, in order to bench test it outside the car, but I continued to adjust the Cable when all of a sudden the Reverse Lights came on. (I placed a mirror in a stand behind the car to be able to see the lights go on and off from the driver's seat and through the rear view mirror). Puzzled, I continued to fiddle with the cable and gear selector and the Reverse Lights kept coming on and off, so obviously they are not dependent on that micro-switch, obviously they are activated by the transmission mounted, cable-activated Reverse Light Switch."
"My apology for any confusion I may have caused anyone, but I should add that there seems to be confusion among technicians and do-it-yourself enthusiasts about the functions of that micro-switch. Furthermore, some XJ's have a 3-wire microswitch and harness, and some have a 2-wire microswitch and harness. It is possible that in later cars, the 3-wire microswitch and wire harness DOES control the Reverse Lights adjustment, but in my 1984 XJ-6, the 2-wire microswitch/harness does not. "
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