Speedometer

[steve_m]

!989 XJR-s.
The speedometer randomly cuts out (rev counter is fine); I understand that there is a relay or module in the boot somewhere, anyone know where exactly?

[ptjs1]

steve,

not sure about pre-facelift cars, but I think the speed interface module is in the boot just above the left rear wheelarch, behind the trim and behind the metal bracing panel.

The module sends a signal to both trip computer and speedo so if trip computer continues to read ok when speedo cuts out, that would seem to imply that its not the module.

Good luck

Paul

[steve_m]

Thanks Paul
Steve

[PaulGover]

I too don't know about pre-facelift cars, but is your speedo the type that's mounted on a single circuit board along with the other gauges? My facelift had a failed speedo when one of the tracks broke, and needed a bit of wire soldered in to fix it. AFAIR, the break was in the narrow part of the board over the top of the speedo, or maybe the rev counter.

[Brakebuster]

i'm 99% sure the speedo has a different signal to the rev counter, as the speedo picks up from the diff on an '89 car for road speed, so how will the rev counter know how fast the engine is going ?

so

it could be the module, it could be the wiring, as there is a connector that can get dislodged, or it could be the back of the cluster as previously mentioned

i would start at the back of the car and confirm the connections ,

if the speedo its self is stuffed, i have a genuine V12 Jaguarsport spare , see the for sale section

BB

[poprivet]

Poor connections on the flexible circuit board behind the gauges are a known weak point, Either at the two multiplug connectors of on the gauge connections themselves. Pay special attention to the earthing points.

It's easy to remove the whole instrument cluster and it will be a chance to replace any black or blown instrument bulbs at the same time.

[steve_m]

Thanks for all the replies, most helpfull.
I'm tending towards a dodgy earth point at the moment.
A chap is coming to trailer the car away up to Norfok on Tuesday to sort out the front suspension, change the rear spoiler and do some paintwork and he also said that he would swap my knackered Momo steering for a decent one; whilst he has that off I'll add the speedo to the list of things for him to check.

[poprivet]

I was looking through Kirby Palm's book for something else and came across his advice for the speedo problem. He says to look at the sensor cable from the diff and see if it has been hardened by heat from the exhaust causing an breakdown of the wire.

I've not heard of this myself but its worth a look.

[BigCatXJS]

On behalf of an existing JEC member (no access to BB at the mo);

Does anyone have any wiring diagrams covering '96 AJ16 XJS speedo?

"I have an unreliable speedo flickers worse when cold. Where can I get an accurate diagram of the cars' electrics? Hard-copy if possible. The book I have is no use for fault finding and does not include the AJ16 at all although it says it includes all 6 cyl models models - thanks"

Thanks, Rich

[P.L]

This site provides some useful information:
http://www.jagrepair.com/JaguarXJSElect ... Icodes.htm

Regards,
Peter.

[BigCatXJS]

Thanks Peter - very handy.

Cheers, Rich

[ptjs1]

Rich,

And remember to prompt the member to buy the proper Jaguar Parts & Service Manual which naturally includes the wring diagrams. IMO, no-one should attempt to run an XJS without spending the money to buy this.

Paul