Cruise control does not work in my 1997 XK8.
The switch at the "J" gate operates in that its red indicator light comes on when pushed. But that is all I get! No speed control.
Where should I start checking?
On the XJ6s I've owned it was usually just the bellows of the servo to the throttle that had a tear or small leak and was easy to spot and replace. Need help on this big move up for me to an XK8.

 

If the red light on the switch has come on have you then set the speed via the button on the steering wheel.

 

You have had 3 post with different electrical issues. I would start at the battery. Check it for voltage, I Believe It should at least 12.6 volts. Then check voltage at fuse boxes. It could be a ground issue also.

On my 99XK8 I had problems with my driver side door. Window and mirror not working. It turned out to be the twist connector where the door wiring connects to the chassis. The ground pin was corroded and not giving the door a ground.

 

On the early XK8s, the cruise control is vacuum operated with a couple of electrical solenoids. Power to these comes from the ECU via fuse #10 (5 amp) in the ECU fuse box.
Check this fuse, and also the vacuum hoses - one from the top of the throttle body, and one from just below the right hand side manifold.


And ............... you are aware of the steering wheel switches ??

 

I have just gotten this car and also joined the Jaguar Forums. Having a number of electrical issues and all the advice will be put to use. The battery is fresh and I keep a "maintainer" on it. The fuses and grounds will be what I attack when I can get up to my shop. Yes, I am aware of the location and use of the CC switches having a multiple of cars with such arrangements. I see some much info on this site that is useful that I figured it was best to start with some questions rather than just dive into electrical circuit checks and tests. The responses can save a lot of time!
I look forward to further communication with members as I get into this car.

 

If you need to dig around in the electrical connections download the JTIS21 from the sticky, there is a multiple step test sequence that will identify the pins.

 

The Cruise Control issue was easy to solve. I got into the engine area knowing how most CCs work and stated checking vacuum lines. Imagine my surprise to find the one under the righter of the engine disconnected. I am now cruising in style! I also am finding shoddy work done by supposedly knowledgeable service people that the previous owners had used (not Jag dealer). Vacuum line for example was snapped off at the Tee fitting and the drivers side switches had been pried out of location rather than removing rubber insert, then the little trim piece under the switch to get at the screw holding the switch. Thanks for the advise on my issues and I will download JTIS21 when I get back to my main computer.

 

Let's hope all your problems are that easy to resolve :-) :-)

 

A great example of the trap that we all tend to get lured into these days - when something goes wrong we automatically start looking for faulty ecus and so on rather than starting with the basic mechanical principles. Not a criticism, by the way - I'm as guilty as the next person!

 

Here is a photo of what I found when trying to sort out a non-functional cruise control on my recently acquired XK8. When weather is cooler I will replace all of the rubber hose sections at the engine. For now I had to rig a new tee with an adapter to attached the different size hose ends.