Speedometer Suddenly Cut Out at the worst possible moment!
 

Try not to laugh!

This Afternoon was really nice and so I thought I'd take 'Cherry Blossom' my Red XJS just out for a little drive and top up with some Petrol.

This was on a Dual Carriageway and I know this road like the back of my hand and all of the quirks that go with it.

Although its a 70mph, I wasn't in a hurry and was purrring along at 60mph but I was well aware of what was ahead.

Which was a number of Traffic Cones, which were parked on the Concrete Strip in the middle of the Dual Carriageway (which were not on the actual road itself)

There was also a Sign that said Roadworks with a 50mph Speed Limit for Safety Reasons.

But apart from the Cones, there was no sign of any Roadworks having taken place and no Workers of any description anywhere to be seen.

Its been like that for Months, with just the Cones and nothing going on.

Consequently everyone is tired of seeing this and no longer take any notice of this 50mph Speed Limit.

And just continue their journey at 70mph+

Except that is for me, because being perceptive, I had a very strong feeling that since this had lulled motorists into a false sense of Security.

One day they would put a Speed Trap there and then catch hundreds of motorists all at once.

I wasn't in a hurry anyway, as just passed this Roadworks aka a line of abandoned Cones, I was about to turn off onto the Slip Road, which is 60mph because it's a Slip Road.

So when I see the Sign for the Roadworks (abandoned cones) coming into View, I just let the Car slow down, so by the time I get there, I'm only doing 50mph.

Which I've got down to a very Fine Art, as this line of Abandoned Cones has been there for Months.

Where because I stick to the Speed Limit, it annoys the hell out of everyone else, simply because in their own heads, this 50mph Speed Limit seems to no longer exist.

Simply because those abandoned Cones have been there for ever and a day.

So Purring along at 60mph, I could see the Roadworks (abandoned cones) just coming into view, so I did what I always do and just let the Car slow down,

so I'm just doing 50mph by the time we get to the 50mph Speed Limit part.

And just to be sure I always Check the Speedometer.

At which point Two things happened both at the same time!

As I looked down at the Speedometer the indication needle suddenly dropped to Zero and Stopped Working!

Then as I looked up the next thing I saw was a 'Speed Trap' Van, on the Verge right in Front of me.

I'm 99.999999% sure that I was doing 50mph but since the Speedometer suddenly Stopped, its not what anyone would call an ideal situation.

Because I always stick to the limit and don't Speed.

How do I get to the Sensor to see what went wrong, do I have to remove the 'glove box' or the whole center Console?

I see that someone else has the same problem.

OB,

There are four components in the chain:

- The shimmed speedo sensor mounted in the back of the rear diff at the top. This sends a signal to the:

- The speedo interface module which is mounted in the boot. This then sends a signal to both:

- the trip computer &
- the speedo

So, the first thing to check is whether your trip computer is reading the distance. If so, it implies the first two components are working correctly.

Then you check if the speedo is reading distance via the odometer or if both the speedo needle and odometer are at fault. If both at fault, it implies the speedo is faulty BUT

I have recently seen a situation where everything worked correctly except the speedo, but the speedo then worked when put in another car. It transpires that (on facelift cars at least) the speedo needs a more robust voltage than the trip computer to work. So it can be a wiring integrity or earth to the speedo itself that is at fault.

So it's out with the multimeter and start working back from the speedo.

Good luck

Paul

I have the same problem and I know my sensor is bad ..... the problem is I can't find the sensor "DBC11116" discontinued. So I guess I got to wait for someone to wreck their Jaguar. So option B is now in play: I am now leaning towards a conversion GPS signal converted so my speedometer can read it. Maybe someone went down this road before who can shed some light on this.

Hi Paul

The Speedo has only ever dropped once but then it picked up again, so this could be a bit of a Nightmare to fault find.

I've also looked in the Boot/Trunk but don't know what the Speedo Module looks like.

Maybe you would be able to identify it from this Photo?

And then if I removed it and gave it a Squirt of Electric Contact Cleaner it might be ok?

On the other hand if its the Sensor, then this looks the job from hell, as you cannot get your hand in there to undo it.

Unless you remove the rear exhaust, or else take the bottom plate off the Cage.

Is the Sensor held in place by Star Keys, I've had a look but its hard to tell.

https://cimg0.ibsrv.net/gimg/www.jag...b7d3e130fa.jpg

https://cimg4.ibsrv.net/gimg/www.jag...7edcc025fb.jpg

Is this 'Black Box' The Speedo Interface Module?

https://cimg6.ibsrv.net/gimg/www.jag...4459718e67.jpg

Do any of these Fuses have anything to do with the Speedo?

This Fuse Panel is underneath the Kneepad underneath the Steering Wheel (UK Car)

OB,

Not sure from your pics. It's a small black box with two sets of wires coming out, one with a black plug on the end, one with a blue plug. See here:

https://www.jaguarclassicparts.com/uk/part/DAC4591

If you do a search on ebay for XJS speedo interface, you'll find lots.

If it's a very intermittent fault, can you check if the trip computer distance recording drops out at the same time? If not, it's probably the speedo or speedo wiring connections. As we all know, intermittent faults are the most annoying!

Cheers

Paul

Hi Paul

Cheers!

I'll have another look Tomorrow in daylight.

And will also Check the Trip Computer, which I never have Switched on.

If I were to have it on would I be able to see it clock up the Mileage on the fly, or do you have to take that reading after you've finished your journey?

OB,

The distance on the trip computer accumulates and changes real-time.

Paul

The speed interface unit is above the ABS ECM and has Speed Interface printed on it. Those do look like the connectors.

It has 2 outputs 1 for the speedo/cruise comntrol and a separate one for the TC, just because the TC is incrementing distance does not mean the Interface unit is working. I killed mine when doing my Cruise Control install, it has a zener diode on each output to protect the counters in the electronics, shorting the output to ground will usually take out the diode.

If your CC works and speedo does not then the Interface unit is GOOD.

BTW the first thing I would do is clean all the connectors.

Hi Warrjon

Cheers!

I've never used the Cruise Control, ever since I've had the Car, so I'll give that a try Tomorrow and then report back.

And I will clean the Connectors.

Just had a thought!

Could it be dust on the Sensor on the back of the Speedo?

I've never seen the back of the Speedo, is it some sort of magic eye like the remote control on a TV?

Would it be a good or bad idea to blast some Compressed Air from an Airline up around that Area?

Could dust be enough to prevent the Sensor on the back of the Speedo from picking up a Signal?

As the fault is intermittent, conventional fault finding sounds like an almost impossible task to achieve.

NO DO NOT blow it with high pressure. Low pressure is ok.

If it's intermittent I would suspect bad connections, 99% of all the intermittent faults I have repaired (in electronics) have been bad connections, either connectors or bad solder joints on the PCB.

This is what I would look for............

- PCB trace (on the instrument cluster) damaged.
- Connection from instrument PCB to Speedo.
- Connector from harness that plugs into instrument PCB.
- Broken wire .
- Wire almost disconnected from pin in plug.
- Corrosion or other foreign matter in connectors.

Hi Warrjon

Cheers!

Does the Speedo actually make Contact with the PCB board or is it in the form of a 'Magic eye'

If it does make actual Contact with the PCB board, would it be ok to spray the board, where it connects to the Speedo with Electrical Contact Cleaner.

Or is there a better way?

How do I get the Speedo out to take a look.

OB
The instrument binnacle has to be removed. The Great Palm's book explains the procedure clearly, and there is loads of stuff on here. The instrument pack has a blue flexible "PCB" that has TWO large multiplugs going into the back of it. These are not easy to get at or replace, but it can be done. Best to remove the steering wheel first before removing the binnacle.
The actual speedo has small bolted connections to the flexible PCB. I doubt the actual speedo is the problem, far more likely, as Warrjon said, the PCB or the connections to it. The copper tracks on the PCB are very delicate and can easily become broken or dislodged where, (eg) the multiplugs plug in. Attached pic shows the back of the binnacle and the rectangular holes where the multiplugs go in, and the other the multiplugs in the dash. The MUST go back the same way they came out. The difficulty is that there is not much loom length to allow easy replacement.


Greg

Hi Greg

Cheers!

Looks like a Fun Job, I'll have a look at Palms book like you said.

OB,

Popping the instrument cluster is much easier than it might seem. It's really a 5-minute job, I assure you. As alluded to by others, I suspect you've just got a slight connection or earth problem on the speedo. The speedo head needs slightly more voltage than the trip computer.

Having said all that, I'd still be checking the interface module connections first. Then I'd wait to see if the trip / cruise works when the speedo drops out. Only then would I start pulling the instrument cluster.

Good luck

Paul

It is getting it back in, with the multiplugs correctly seated and not having pushed the copper contacts out of line, that I find hard, Paul! Maybe my car is a bit shorter in loom length to the plugs than most?
Greg

Oh me, no speedo? Not a big deal. Just peek at the tach.


Carl

Hi Paul

That sounds like good advice but do I have to take the Wheel off?

Hi Carl

The Tach works fine and although I used it as a guide, the Speed limits are constantly changing, along the Country Roads where we go tripping.

So I'd rather have the Speedo working properly.

OB,

Just move the wheel as far down or as far out as you can. I think you've just got the reach adjustment on CB(?) so adjust the wheel towards the seat.

To take Greg's point, perhaps the looms are a bit tighter on pre-facelifts, but slim hands also definitely help! On a facelift, it helps to tip the cluster forward from the top and then reach in to carefully disconnect the plugs. I suspect the same principle applies on earlier cars.

Paul

Hi Paul

Cheers!

If it goes again, I'll check the Cruise to make sure the module is working and if it is then I'll pull the Binnacle out and clean the Contacts.

It sounds a breeze when compared to having to take out that Sensor from the IRS.

Easy solution here OB...

Get your phone out of your pocket, install a GPS speedo and stick it to the dash. Done-did :D

Hi Daim

I've never heard of a GPS Speedo!

Have you got any more info.

But who knows, I may be able to get the Proper one working.

Would a GPS Speedo be regarded as a 'Bodge'

OB,

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.

Paul

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.

Hi Paul@Warrjon

With what little I know about Auto Electronics, I'm already thinking you're right it must be the Cluster Connector Plugs.

So would it be a case of unplugging the Cluster Connectors and then just plugging them in again

Or unplugging the Cluster Connectors and then Spraying them with Electrical Contact Cleaner before Plugging them back in.

Or another way that I should do this?

OB,

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?

Cheers

Paul

Hi Paul

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.

Do you think a bad earth could be the Problem?

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

The speedo in my lump is waky. I have the module to fix it and how to do it. But, way down on my task lists.


I measured the error in two ways. Each with a different result !!!


1. I compared my indicated to one of the cop radar trailers one sees around here is suspect areas. My indicated 49 MPH is their 25!!!


2. I revived my ancient TOMTOM GPS. It says 25 when my speedo says 35!


3. My SOP tends to favor #2.


But, no matter, I just watch the tacho !!!


But, to me, an in out fault says bad connector somewhere along the line either hot, signal or ground.


And electrickery is not my best skill.


Carl
Carl

Hi Tom@Carl

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.

https://cimg8.ibsrv.net/gimg/www.jag...ceda25d332.jpg

Rear View of the Binnacle that holds the Speedo and Tacho

(This ones off my Parts Car)

Does the cruise control work? if so the speed interface unit is working and you problem is in the instrument cluster.

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.

Cheers,
:icon_toast:
Ken

Hi Ken

Cheers!

Good advice indeed but I cannot get the Binnacle out until I've lowered the Steering Wheel

If push came to shove I probably could but it would be a bit of a squeeze and I don't want to graunch the dashboard.

But again we've been out tripping all day, just like we did Yesterday and the Speedo is still working!

So a part of me is now very reluctant to touch it, in a 'if it ain't broke don't fix it sort of way'

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!

Tempted mate? Cheers,
:icon_toast:
Ken

sorry wrote on wrong topic

Hi Ken

Been to OZ lovely place and went Surfing on Bondi Beach.

'Correction' Hired Surfboard-saw the size of the Waves, stayed on the Beach.

Decided to go Swimming!

'Correction' Would have gone Swimming but unfortunately went to that Aquarium in

Manly and saw the Size of those Sharks.

Decided Not to go Swimming.

There's always a downside:icon_omg:

As I've mentioned many times, without the help from 'Greg' and 'The Wizard'

PTJS@Doug@Daim and many others on this Forum.

My Car would still be in the Garage mouldering away.

Also thanks for your help with the Speedo.

Would love to take you up on that Trip but having more Fun than I know what to do with!

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, coupled with the Sweet Aroma of a Wood Burning Fire

(or was that the Brakes!)

While Purring along in my Car 'Cherry Blossom'

I could go on but I'm sure that you get the idea........

Hi Guys

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.

:icon_lolsign:

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 . . . :icon_omg: It's worse than I thought . . . far, far worse !!! (much snickering; off-stage right)

Cheers,
:icon_toast:
Ken

Hi Ken

Unfortunately its true!

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!

https://cimg4.ibsrv.net/gimg/www.jag...bdf0db3490.jpg

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!

https://cimg8.ibsrv.net/gimg/www.jag...13a0363ebd.jpg

'Needlessly' Removing the Plastic Cover round the Steering wheel to try and find out why the Steering Wheel wouldn't drop down!

https://cimg2.ibsrv.net/gimg/www.jag...215acc3516.jpg

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!:icon_dunce:
Come on Guys admit it, we've all done something like that! haven't we...........?:icon_frown:

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'