Now that the spring is here and my Kitten is back on the streets, I thought to start troubleshooting with the cruise control.

There are days and weeks that it works like charm, but without a warning after disengaging it it just refuses to get back to work. Holding the set button tightly down it keeps the current speed (or lets it slow down very slowly) and when released it disengages completely. Then after a while it works again like it would not have given anygrief ever.

Kay

{edited the topic as I seem to pour all the problems here}

 

Kay,

I see there hasn't been a response, and a quick search of this forum doesn't produce any like threads, though that is subject to key words being same.

From you description is sounds like a switch connection issue. Hopefully someone will chime in that has taken the component out of the casing, possibly a solder joint misbehaving.

The cruise control is not commonly known to cause a problem. Here is the exploded diagram of the component. There is just one screw on the underside of the dash. Remove and inspect to see if anything stands out.

Facia Switch Panel-From (V)594576 - Parts For XJ6 (2.9, 3.2, 3.6, 4.0) from (V)500001 to (V)667828 | Jaguar Classic Parts UK

 

Hi Kay,

Your symptoms do sound more electrical than vacuum-related, and like Rob I haven't heard of problems with the Cruise Control switch, but it would be worth having a look inside to be sure the contacts are clean.

A common issue is the dump valve, which is mounted on the left front fender well below the inlet horn for the air filter housing. It is an electrically operated solenoid valve that immediately releases the vacuum from the cruise control system when the brake pedal is applied or the cruise control switch is turned off.

I think I recall that as a safety measure, the dump valve's normal position is open, and it must receive 12 volts in order to close so the cruise control system can hold vacuum and operate properly. Perhaps your dump valve is beginning to fail, or the electrical connector is loose or corroded, or the ground stud on the left inner fender is corroded and the dump valve's ground connection is intermittent.

It would be worth disconnecting the dump valve electrical connector and cleaning it with a small wire brush and zero-residue electrical contact cleaner spray (not WD40). Also remove the nut from the ground stud, pull off all the wires and clean their ring terminals, the threaded stud, and the nut and any star washers (note where the star washer is positioned). Use a small wire brush and flush all the parts with electrical contact cleaner, let them dry, then reassemble. The nut should be tight but not so tight that you break the stud off the fender....

Another possible cause is the brake switch - if it is actuating even when you are not depressing the brake pedal, you won't be able to operate the cruise. The next time you can't operate the cruise, you might pull over and put the car in Park, leave the engine running, and get out to see if your brake lights are illuminated even though you're not pressing the pedal.

Other possible causes are a leak in a vacuum hose or the cruise control actuator bellows (the black rubber device above the intake manifold on the left side of the engine as viewed from the driver seat). The actuator connects to the cam on the throttle body via a metal linkage, and a leak in the bellows can cause the cruise control to be inoperative. Given the intermittent problem with your cruise control, I don't think this is your problem.

Those are the things I can think of off the top of my head. Check them out and let us know what you find.

Cheers,

Don

 

P.S. Kay, for the future, it would be helpful if you could add your location (at least your country) to your signature line, so others can offer advice that may vary according to country environmental regulations, Left-Hand Drive or Right-Hand Drive, etc. I don't think it matters for your cruise control issue, but for other issues it can matter a lot.

Cheers,

Don

 

Thank you for the helpful tips, I know one thing it is not and that is the brake switch. I am almost neurotic to have all the lights working properly and I do check them from time to time.

But there were very good tips, I will get to it probably next week as this wknd has been fully booked with other activities and my Kitten will be left at home (alone) anyhow

Kay

 

Hi Kay,

Since the problem you describe seems to be intermittent, it is possible that your brake lights are coming on when you are not standing behind the car to see them, so it would be worth checking them the next time your cruise control misbehaves.

Cheers,

Don

 

Thanks Don,

I actually thought of that as I was driving today, naturally it worked like a charm all the time. So I will check next time it might do that.

But I had an new thing that I found, none of the instrument lights work (all the warning lights and gauges work) . As I know they have not been changed since 2005 at all so it can be that all of them have burned, but as I know my Kitten I know it most probably is nothing that simple.

Kay