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It won't be the sensor, IMO. They are pretty reliable and the worst I've seen is a fluctuating needle if the air gap has been disturbed, such as when the diff is rebuilt (I know this from experience!). IMO, those sensors work or they don't work (same with the interface module). They don't drop out and then come back. That's an intermittent voltage drop you've got, I'll bet.
I agree it's unlikely to be the sensor, VR sensors are very reliable, a fluctuating needle won't be the sensor, the interface unit has a schmitt trigger to prevent this. It works down to IIRC 1v p-p wave then the pulses from the interface unit just stop.
Instrument cluster is not difficult to remove, although I remove the steering wheel as it makes the job easier.
Check the connectors at the interface first, but my guess would be the cluster connector or PCB.
I'd suggest looking at the wiring diagram and finding the power feed that goes to the speedo. It's clearly shown which wire it is. I know it on the facelift diagram but not the pre-facelift. Check the integrity of the wire on that pin first. Then look at the PCB and trace along the PCB connections to the speedo and look for any tiny breaks. Then check the connections on the plug.
I don't think you mentioned exactly what happens when the speedo goes out? Does the needle drop right out or go down to zero or bounce? Does the odometer continue to increment when the needle goes out?
When the Speedo Stops Working, the Needle just drops down to Zero and does Not bounce but then about half a mile down the road, it will start working again.
As for the Odometer, I can't say that I ever look at it, but will do so if the Speedo drops again.
There is no pattern to it and I never have the Trip Computer on.
Hey Alex,
I am in the same boat as you my speed indicator is not working (bought it that way) but the RPM gauge is working. Mileage is not being recorded or the push button trip is not work also. I have located the speed transducer interface followed it to the trans .... hard to get under car as last owner lowed it. I am waiting to see how your pulling of the speedo turns out for you.
Should I throw caution to the wind and just replace the interface .... if it doesn't fit it a got a part when it does fail.
When it comes to Auto Electronics, 'Warrjon' is 'The Man Who Can' along with Greg and Grant.
As for me I haven't got a Clue and totally hopeless at following things like Circuit Diagrams.
Tom: I wouldn't go throwing Caution to the wind, as that could be a very 'Expensive Option'
Taking out the Binnacle for the Speedo and the Tacho is no more than a Ten Minute Job but make sure that you have got room behind the Steering Wheel to get it out.
And do be extremely Careful with the Flexible Printed Circuit that the Plugs Plug into, because AFAIK replacements are NLA.
After I had a Practice taking the Old one out of my Parts Car, today I tried to do the same on 'Cherry' but because I couldn't lower the Wheel on my 1990.
Trying to get it out of the Car, would have been a bit too close for comfort, so I had to be content to jiggle the plugs about and hope for the best.
We've been out 'Tripping' all day long and the Speedo has been working Perfect but when I find out how to lower the Wheel, then I'll do a proper cleaning job.
It could be something as simple as 'Unplugging and Re-Plugging' the Two Multiplugs.
That is 'sort of what I did' and its been working Perfect all day long.
Rear View of the Binnacle that holds the Speedo and Tacho
Hey Alex,
I am in the same boat as you my speed indicator is not working (bought it that way) but the RPM gauge is working. Mileage is not being recorded or the push button trip is not work also. I have located the speed transducer interface followed it to the trans .... hard to get under car as last owner lowed it. I am waiting to see how your pulling of the speedo turns out for you.
Should I throw caution to the wind and just replace the interface .... if it doesn't fit it a got a part when it does fail.
thanks
Tom F
Does the cruise control work? if so the speed interface unit is working and you problem is in the instrument cluster.
. . . do be extremely careful with the flexible printed circuit that the plugs plug into, because AFAIK replacements are NLA . . . I had to be content to jiggle the plugs about and hope for the best . . . but when I find out how to lower the wheel, then I'll do a proper cleaning job. It could be something as simple as 'unplugging and re-plugging' the two multiplugs.
Good advice here, OB. Putting aside the relatively fragile nature of the printed circuit film and the foil "tracks" on it, this type of bared copper finger connections, as shown in your pic, which make contact by insertion of a plug are notoriously subject to verdigris or corrosion. Wiping both fingers and plug contacts with a swab of electronic cleaner will provide a lasting fix . . . avoid abrasives!
An even more common cause of failure in this model specific and well known area of weakness is caused by a combination of inadequate length and flexibility in the looms to plugs, coupled with lack of a positive plug retention device . . . they are known to simply fall out. So, easing the loom path and avoiding nearby physical interference are wise moves.
Smart move OB . . . very smart, mate . . . sleeping dogs, eh?
So, now freed from chasing that fix and frustrated by having so much free time enjoying dat purrin' puddy-tat . . . what are you like at welding in new floors? Body mods? Spray painting? With a bunch of work and parts, my project XJ-S now runs well . . . although still without most of the exhaust system, it growls rather loudly. Strangely, after so much time and effort, my "to do" list appears to have grown - LOL.
Having followed your restos in detail (worried there would be questions), if either you or Greg in France fancy a "no expenses paid" trip to Oz, I am sure I could persuade Grant to chip in! Bring a prodigious thirst as I have a vast supply of very good wines . . . and an even bigger supply of not-so-good that I have found excellent at cleaning Jaguar wheels . . . hmmm, best not to spill it on paintwork though!
After Two Great Days Out with the Speedo behaving itself, there was a moment when it dropped but only for a Second before it recovered again.
This was making me nervous because on most of our Trips, the Speed limit constantly changes so you always have to keep an eye on that.
I mean who on earth would believe your Speedo stopped working!
In view of this the only way was to pull the Binnacle out and try and try and do the Job Properly, or at least I would have done except for one small problem.
The Steering Wheel wouldn't drop down enough to pull the Binnacle out, because there was no resistance on the lever that drops it down.
Maybe it was a broken wire or something like that but when I pulled the cover off, I couldn't see anything wrong.
Though what was even worse than that, was the GF managed to fix it all on her own!
The full Story of how 'SHE' fixed my Car, will be on my 'Cherry Blossom' Restoration Thread, although I know its going to be extremely painful to have to write this up.
Hi Ken. Yesterday was one of the Best days we have had all year! With the Sun bursting out of an Azure Blue Sky, Autumn Leaves falling out of the Trees . . . I could go on but I'm sure that you get the idea . . .
Hahahahaha . . . Yes mate, they tell me Spain is quite beautiful at this time of year !!!
Gosh . . . we are all hoppin about like bunnies at a chicken only barbeque here waiting for the the explanation of . . . wait for it . . . HOW MY GIRLFRIEND FIXED MY CAR . . . AND A DREADED JAGUAR V12 AT THAT !!!
Are you serious mate? . . . I mean why not gloss over it and move on? I think any such admission deserves being forced to return the Grant Francis Golden Underpants Award for Technical Incompetence which you were dubiously presented for your resto thread . . . forced to stand in the sleet & snow until the English Winter arrives to brighten things up . . . then asked, on behalf of an admiring audience here on the forum, to pass on to your (obviously far brighter) GF, our invitation to a Grand Investiture Ceremony . . . where your Public Apologia will be read out to the masses for their ribald amusement . . .
. . . or . . . hell, should we just feed you to those Bondi sharks where tourists are always on the menu?
I wish I could say we have all done foolish things . . . taken life with a Jaguar just a little for granted . . . or at times, even been upstaged by those we love the most . . . but then . . . truth is . . . no; we haven't !!! Gosh, having admired you from afar for so long in your endeavours with Cherry, I feel so let down. Perhaps Grant or Greg can suggest a cure . . .
Addendum . . . It's worse than I thought . . . far, far worse !!! (much snickering; off-stage right)
Cheers,
Ken
Last edited by cat_as_trophy; 10-20-2017 at 02:24 AM.
Reason: addendum
The knob that adjusts the rake of the Wheel, only seemed to move in one direction and never in a million Years did it ever occur to me to pull it backwards.
Obviously you think I am making this up but I can assure you I'm not and as they say in the all the best 'Bloggs' I've got the Photos to prove it!
The Knob that adjusts the rake of the Wheel only ever seemed to move one way, er....that's the wrong way by the way!
'Needlessly' Removing the Plastic Cover round the Steering wheel to try and find out why the Steering Wheel wouldn't drop down!
Even with the Cover removed where you can see those two big Springs, it never once occurred to me to pull that lever in the other direction!
Then to make things worse if they can get worse, the GF jumps into the driver seat where not knowing any better, She pulls the lever and 'Bingo' the Wheel drops down!
Come on Guys admit it, we've all done something like that! haven't we...........?
My only hope of Salvaging any Credibility, would be in fixing the Speedo, although on second thoughts, I may as well let the GF loose on that one as well!
If I can ever manage to get her out of 'Smug Mode'
10-10-2017, 12:13 PM
