1990 Speedo Transducer Location
 

My '90 Speedo is bouncing all the time...sometimes at zero, sometimes working. I have read that the likely cause is the transducer. I want to check the wires/connection, but can't locate it...can someone post a pic of its location?

Is it easy to get to without a lift?

If it is the same as the '89 model then the transducer is on the rear of the diff; it looks like an ABS transducer.
More likely to be the culprit is the interface unit which is located in the boot/trunk; it is next to the interior light below the wing/fender.
It is a little black box; it might be worth just cleaning the connectors as they are hard to come by.

Hi Kariblay

No, that Shiny Black Box above the Battery is where the Relays are kept

The Box for the Transducer 'Thingy' is on the other Side of the Car inside the Boot/Trunk and up under the Fender/Wing in a very hard place to get to unless you are a Contortionist

The Transducer is in the IRS and even harder to get to, 'if that's possible' you can recognize it from its very thick wire going into the Boot/Trunk

Just as likely an even more likely IMO are the Multi Plugs that go into the Instrument Binnacle

But be extremely Careful that you don't damage the Printed Circuit that these Multiplugs Plug into

I had the Same Problem when my Speedo Stopped Working and this is how I Fixed it with a little help from the GF

https://www.jaguarforums.com/forum/x...122634/page76/

Hi Kariblay

I cleaned the Tangs on the Multiplugs and the Sockets they go into in the Printed Circuit
but do be extremely Careful you don't damage the Printed Circuit when you do so

My Speedo had suddenly stopped working for no apparent reason but when I cleaned the Plugs and Sockets everything started working again and is back to normal

Its not a difficult job to do you just have to watch what you're doing and be Careful

Hi Kariblay

I am not an Auto Electrician or an electrical Genius like 'Warrjon' so there could be a number of reasons why your Speedo isn't working and mine decided to suddenly drop out

So faced with the choice of paying a 'Shop' to fix it, where they could charge you 'megabucks' I decided to try and fix it myself

There are 3 Main places where there could be a fault but that is not exhaustive, as you could have a faulty component or maybe a bad earth or it could be something else entirely different

So I decided to tackle what I considered to be the easiest first (others may have a different view) but I decided to take the Instrument Binnacle out

I was a little bit scared of doing this, as I have heard horror stories of those who have damaged something to such an extent that the Speedo will never work again

So you have to be REALLY CAREFUL not to damage the printed circuit because you cannot but another one

This is not a 'Big Hammer Job' you need to be as Careful as a 'Watchmaker'

You don't have much slack on those Multiplug Leads and its quite hard to see what you're doing

But basically there are 2 Multiplugs that plug into the back of the Printed Circuit which is attached to the back of the Instrument Binnacle

So once you've undone the Screws that hold the Instrument Binnacle in. you then have to VERY CAREFULLY ease it out of the dash as much as you dare

And then reach in with your hand in order to CAREFULLY disconnect (ie pull out) the 2 Multiplugs that are plugged in to the Printed Circuit

After which you can Pull the Instrument Binnacle out and then once having done so you can CAREFULLY clean the Multiplugs and Sockets

There is a Step by Step Guide of how I did this including Photos on my 'Cherry Blossom' restoration thread

And here is a link to that Page https://www.jaguarforums.com/forum/x...122634/page76/

This is Not a guaranteed fix but it worked for me and now my Speedo is working as it should be

But you could equally have a fault with the Transducer or the little Black Box in the Boot/Trunk which is tucked under the Wing/Fender

I didn't go near either of these because I decided to have a look at the Instrument Binnacle First and although this fixed it for me, it might equally not fix it for you

If you are still unsure about this I would get some advice from 'Warrjon' and 'Jay Jag Jay' has also done the fix from the Transducer

At the end of the day its really you're call which way you want to go but if you decide that you want to pull the Instrument Binnacle out be VERY, VERY, CAREFUL, not to damage that Printed Circuit!

Does the trip computer and cruise control work, if so then your spped interface unit is ok and the problem is more than likely in the cluster.


If this is the case then pull the cluster and clean all the connectors. There are other things but do these first.

The easiest way to get the cluster out is to remove the steering wheel.
Mind you, mine doesn't have an airbag.

On my 89 V12, the bouncing speedo required a new speed transducer. Once I swapped them, speedo is back to normal.

I didn't have any particular problem changing it, you screw the old one out, screw the new one in, and reattach the wires. No adjustments or calibration.

The only "difficult" thing about the swap on mine was jacking the car up (just one side) to be able to access it.

Thanks,

John
1987 XJ-S

Fat fingered, mine is an 87, not an 89.

John

Hey JCR...

Wondering. Where did you find your transducer? I have been chasing a speedO problem for a while and I cannot seem to pin it down... How did you know your transducer was bad?

I have replaced the cluster, cleaned (to the best of my ability) the connections. Opened the transducer I have (looks fine) and removed the sensor at the dif and still,,, NO luck. NO love and NO reading... PITA

Removing the sensor doesn't have to be hard btw... If you are willing to glue or seal them back into place,,, simply remove the two "PAINT CAN CAPS" (thats kinda what they look like) just under the shelf for the gas tank - under the spare tire. Took me about 5 - 10 minutes to remove it. Just pry the innermost two body plugs (paint can caps) off and replace after.

Just found THIS as well... Its something I needed and thought maybe Y'ALL might as well... Im checking it out as we speak.

My problem is I have NO idea and NO specs on testing these components...

I am completely lost in this quest for ME speedO. Stinks.

Hi Jay

If your Trip Computer is reading the same Mileage as the Mileometer on the Speedo (give or take a couple of miles)

Then that would seem to indicate that the Interface Black Box 'Thingy' in the Boot/Trunk underneath the Wing/Fender is OK

So that's one little test that you can do

https://cimg6.ibsrv.net/gimg/www.jag...5e6d53d131.jpg

The Speedo Interface 'Black Box' is inside the Boot/Trunk underneath the Fender/Wing
I couldn't get the Camera far enough in there to get a Photo but if you follow the thick wire from the Transducer in the IRS you should eventually find it though it isn't one of those things in the Photo, its further back than that

hey OB... I get nothing when it comes to trip info, odometer or speedo...

honestly,,, I havent traveled enough in her to KNOW about the dash trip computer....its a good point...

Hi Jay

It's gotta be worth a Shot If your Trip Computer reads the same as your Mileometer then the Black Box 'thingy' should be ok and if the Cruise is working as well, well that is even better!

I didn't really *know* that the transducer was bad, as there seems to be no electrical test (at least with my limited equipment) to confirm or deny it.

After my new transducer arrived, I tried various voltage and resistance measurements, and compared them to the "old" transducer, but nothing made a lot of sense. So, I put the new transducer in and *presto* speedometer is working as advertised.

I had pulled the instrument cluster and cleaned it up a few years ago, so I didn't think that was likely the issue.

I was hoping to come up with a definitive test...put meter lead "a" here, "b' there, and if you don't get "c" on the multimeter it's definitely the transducer. But no luck.

Thanks,

John

Hi John

That is exactly why I decided to remove the Speedo Binnacle First, as speaking as someone who had never done that job before it only took 10 Minutes to take the Binnacle out

Then after about 2 Hours of Very Careful Cleaning, I put it back and took the Car out for a Test Drive where the Speedo was working perfect

But imagine what would have happened if I had gone the other way and spent $100 on a New Transducer (or what ever they are)

In my case a new Transducer would have not made any difference and that would have been $100 dollars down the drain

Because in 'my case' the problem was down to a corroded contact in the back of the Speedo Binnacle

So from a personal point of view, I would always much prefer to do exactly what you did and clean up the Contacts on the Speedo Binnacle first

Then at least you can eliminate that as being part of the problem before you start spending money on Components you don't need