My speedo keeps dropping to '0' at around 30 mph. It stays there until I stop, then some of the time it will operate correctly after starting again. Do any of yo know where the speedo gets it's signal?
The cruise control works even with the speedo showing '0'.
Thanks for any advice.
RagJag

 

Ragjag,

A late XJS takes the speed signal from a sensor mounted in the rear of the diff. The number of thin plastic shims located between the flange and the diff is critical to maintaining the correct air gap.

However, because you seem to have an intermittent problem, I would look first at the connection to the instrument cluster and secondly at the speed interface module which is in the boot.

Good luck

Paul

 

My speedo was intermittent, it would start and stop. I realised after preliminary investigation I may have an electrical problem somewhere.
I first removed the instrument cluster and remove the two main multi pin connections. It is there I noticed the male plug had some black oxidation on the pins. Removed black oxidation and problem solved

 

ptjs1, is the interface module you mentioned as being in the boot the tranny module beside the top relays?
RagJag

 

RobertL, is it difficult to remove the cluster? I have not done so and would like an idea of what I will have to remove to get the instruments out. Thanks.
RagJag

 

The cluster is pretty easy to pull, but I only have experience with my '88. There are screws to the left and right of the cluster as well as one under the top of the cluster (this can be rough with a long-handled tool.) These screws will allow you to work out a plastic surround that helps secure the cluster in place.

There are little caps on the warning light row just outside the turn signal indicators that pop off, and behind each is a "near" screw and a "far" screw. You want to undo the "far" screw (you'll see what I'm talking about.)

Coax the thing forward, make sure the steering wheel is fully extended towards you (and tilted down - your year has tilt, right?) and once you get the whole contraption towards you, reach behind on the right and disconnect a pair of large connectors. On the long ends, you should be able to find a clip to pinch that will let you take them out. You can just slip the whole thing past the steering wheel at that point, the treasure is yours to take.

Get some electrical contact cleaner (applied sparingly) something to scuff the corrosion off of the contacts with - some pencils have a coarse eraser, which is handy, but I ended up using 800 grit sandpaper as gently as I could.

There are screws on the back of the assembly that might also have some corrosion. I intend to at least loosen the ones on my cluster to clean any corrosion present (this can also assist in helping your gauges read true if you think they're off) but I'm hesitant to remove them completely.

I had an intermittent speedo problem recently. I'd just replaced my gauge lights with LEDs, and every so often my speedo would tank (and along with it my odometers would cease working) and my temperature gauge would simultaneously spike. Happened on and off for a couple days, but haven't had an incident since.

If any of my instructions for the removal of the cluster are incorrect, please put me in my place - I have no experience with facelift years.

 

Ragjag,

No, the speedo interface module is a small module on the left side of the boot. See here:

Trunk Mounted Relay and Fusebox - Parts For XJS from (V)179737 to (V)226645 | Jaguar Heritage Parts UK

The removal of the cluster is close to the way StargazerXJS described. However, it sounds as if the top 2 screws are different on a facelift. It's all described pretty clearly in the Parts & Service Manual.

Good luck

Paul

 

Thanks to all and I will post the result of my mucking around behind the cluster.
Cheers, RagJag

 

I removed my speedo cluster today and polished the contacts with a small wire brush in my Dremel, applied a very thin film of dialectic grease to them and re installed. I hope this fixes the speedo dropping out. If not I will explore other causes.
Thanks all for your help, especially RobertL
RagJag.

 

STARGAZER: The instructions between what you proved RAGJAG and a FACELIFT XJS is very different. But you are right on the money ...............Those contacts on the two plugs build up a a coating that interferes with some of the gauges. Those plugs are not sealed and exposure to
moisture/ air and over time makes them vulnerable and maintenance should be done by all owners.
I hope all is better RAGJAG.

 

Many thanks to Stargazer and RobertL. So far the speedo has not quit again. I did have a little problem removing the unit because I missed the step of removing the top two screws at each corner of the cluster. I also had not read Stargazers post at that time, which proves the truth of the old maxim, 'read the instructions after all else fails'.

Finally, after much fiddling the little cover over the screw popped off and there it was. Getting the large wire connectors off was a bit difficult. I made a tool to reach behind the connector to put pressure on the lower clip. 3/16" rod was used for that.
If I have another speedo drop I will check the interface in the boot.
Cheers, RagJag