[xj-s] 1990 XJS, speedometer and odometer don't work

It started with intermittent issues of the speedometer couple of
months ago, now both Speedometer &n Odometer don’t work. What
should be the cost to mrepait those (fix and maybe replacment)?
Thank you.–
jack99
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In reply to a message from jack99 sent Tue 20 Aug 2013:

The first thing I would do is pull the instrument cluster and check
the condition of the flexible printed circuit on the backsides.
Sometimes the foil at the connector comes loose from the plastic
and bends sideways, or even breaks. Be careful when you reinstall
the plugs (2) into the back of the cluster, that they go straight
in.

If you need a replacement, Norman Motors might have one. I bought
one from them 2 years ago.–
The original message included these comments:

It started with intermittent issues of the speedometer couple of
months ago, now both Speedometer &n Odometer don’t work. What
should be the cost to mrepait those (fix and maybe replacment)?
Thank you.


1991XJS Classic Coupe
Deltona, United States
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In reply to a message from jack99 sent Tue 20 Aug 2013:

Is your the model where the signal is generated from the diff?
(identified by a sensor and cable leaving the diff, routed to the
boot,) Then I would check the voltage to the electronic model thats
mounted on the underside of the top rail in the boot.–
The original message included these comments:

It started with intermittent issues of the speedometer couple of
months ago, now both Speedometer &n Odometer don’t work. What
should be the cost to mrepait those (fix and maybe replacment)?
Thank you.


Phil.D 3.8 etype, XKR, XK150 FHC
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–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

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Hello jack99 - what did you do to fix your non-working speedometer and odometer - I have this problem now (noticed that you posted this in 2013, but did not find any posts with your fix) - posting this reply 12/28/2019.

Tex Terry
1986 XJS V12 Coupe
1991 XJS V12 Coupe Classic

I have a 93 XJS, and my speedometer and odometer stopped working.

It turned out that my rear differential was low or almost out of oil.

I discovered this when I replaced the speedometer sensor that goes into the rear differential on my vehicle.

The output of that sensor, goes into a small computer module in the trunk, which reads the electric signal from the sensor, and puts a out a different signal. From there, the wire goes to the front, where the dash board speedo is operated by an electric signal.

That’s how it works in my car. Yours may be different. :slight_smile:

Yes, on my 91 coupe the setup is the same - did the replacement fluid fix your problem, or was it a bad sensor at the diff?

texterry,

I think my problem was just that my rear diff had no oil.
When I first replaced the sensor, the speedo still didn’t work.
When I filled the diff with oil, it did work.

In terms of diagnosis, I wasn’t sure what to do.
The speedo only puts out a pulse while the wheels are turning, so I didn’t know of a way to drive and try to tap into the wires to look for a signal. Plus, I don’t have an oscilloscope, although I was looking into buying some inexpensive ones off ebay that interface with a laptop computer.

The idea of putting the jag on jack stands, removing the rear tires and “driving it” like that, just didn’t seem safe to me… plus where I live, I really didn’t have a good place to do that type of work… it would draw too many stares and probably complaints from the the neighbors.

So, I fixed it the expensive way :slight_smile: – Parts swapping.

It seemed most likely (at least to me) that the component in the trunk on the driver’s side went bad. It’s a small box that connects to the sensor coming from the differential. It reads the electrical signal from that sensor, and creates a different electrical output signal which is sent to the speedometer gauge. I don’t know anything about any of the signals… that’s why I was considering getting an oscilloscope.

Instead, I bought “another” box used off of ebay, and tried it. Nope. Still didn’t fix my problem. Of course, there was a chance that both the old part and the used part were both bad, but I moved on to the sensor itself. Bought that off of ebay. Cleaned it up some with windex and paper towels, and installed it. The sensor bolts to the rear of the rear differential. It’s somewhat high up, above the oil fill screw. The wire runs under the car, and through a hole in the bottom of the boot, where it is sealed with a grommet, and then an electrical connector plugs into the box that I was describing earlier.

The sensor is held on by two small bolds. maybe they were 5/16" in size… I don’t recall.
It was difficult to get to the bolts, but using a flashlight and some patience I eventually got it.

It would have been easier to get to if I had removed the cross-bracing and a metal plate from the rear of my XJS convertible, but I didn’t want to be bothered.

So, that’s a description of how I got my speedometer working again. Parts swapping until it worked again! I figured it could work, and would save me the money of buying the oscilloscope… plus, save a lot of time, assuming that it did work out.

    -Phil

I have never bothered to look this up… BUT the spacing from the sensor to the machined surface inside the rear diff that it “senses” matters. Frequently there are little plastic shims under the sensor. Too many shims / spaced too far out, it might not work. There is probably a spec in the ROM.

I had the failed tach problem years ago, turned out to be the black box in the trunk, FWIW.

I don’t see how oil level would matter at all. But I can’t guarantee that.

What I can guarantee is that running a diff on low oil is never a good idea and will get noisy and expensive, in that order.
Regards
Bob

Agreed on the low/no oil. I had no idea it was low!

Not sure how or why, but that was my experience. Maybe it’s what you said about distance. Maybe when I first tried it, the sensor was too far away, but after I put in the oil, I tightened everything down really snug, so the sensor was properly positioned.

That actually would be a good explanation. Yes, you are right that there were several washers or spacers of some type. How ever many were there, I kept them and reused them.

Regarding the low oil, I think I just got luck! However, I will say this… after having fully drained and and then refilled my rear diff just this past weekend, I sure wish that it didn’t leak! I don’t know what’s involved in rebuilding this part of the rear subframe, but I guess eventually I’ll have to learn!

    -Phil

Hi Phil-
Lots of possible leaks, most common is probably output shafts, then pinon seal and diff cover. Lots of stuff in the archives about all of these. None of them are that much fun to fix :frowning:
-Bob

I’d think it more likely that you bumped a connector while filling the diff.

Maybe.
Found my speedo is getting a signal.

The problem that I have now, is that I had to remove the instrument cluster as part of replacing the A/C evaporator coil, and in the process the very brittle plastic in the instrument cluster broke where the wire connectors plug in… so now I’m trying to acquire a replacement one – part number DAC11157.

Would you be able to post a pic of the area of the broken connector - just curious how it would break - thanks - Tex Terry II 1991 XJS V12 Classic Coupe, 1986 XJS V12 Coupe - 2/16/2020 1619hrs EST USA

Here’s a photo from the web that I marked up to show the issue.
I added the purple lines as guide lines so that you can see what I’m referring to.

There are two connectors on the instrument cluster. Each connector looks symmetric, but it’s NOT.
The connectors have two clips built in, one on each end, and ONE of the clips is the full width of the connector, while the other clip is slightly narrower.

As a result, the connectors have a right way to connect them, and a wrong way where they won’t fit.

I think that I tried to install the connector the wrong way, which seems like it will fit, but really never would. Now, my plastic was very brittle, so that caused the plastic itself to crack and break.

Adding to the problem are two more issues: First, it’s difficult to see when you are plugging in the connectors. I didn’t think to try to use a mirror to see better, but that might have been smart.

Second, for one connector, the side with the larger tab goes on the top, and for the OTHER connector, the side with the larger tab goes on the bottom. So, you need to know which connector goes which way (in terms of up or down) and be sure to plug them both in correctly.

I used a piece of masking tape and wrapped it around one of the wires that goes on the “top” for each connector so that I wouldn’t make the same mistake again.

-Philip

Wow, that is easy to mix up. Luckily the earlier ones (on my 88 XJS), both connectors have one less electronic tab on one side (i.e. 7 on one side, 6 on other), so it’s easy to know if you’ve got it lined up right or not.

I always work from the far right (center of car), peaking into the back of it as I try to hook them up.

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Guess I was just lucky while working on my instrument panel - the wire bundle, for each plug, kept it’s shape so that I did not plug back in the wrong way to each socket - thanks for the pic and description of the tab sizes - I will take note of this when I go back in to continue my work on the instrument panel - Tex Terry II 1991 XJS V12 Classic Coupe, 1986 XJS V12 Coupe - 2/19/2020 2127hrs. EST USA.

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I’m guessing what’s broken isn’t the flexible circuit but rather the plastic housing underneath it. Perhaps someone here has a spare.

If all else fails, what you could do is buy a couple of generic Delco connectors with enough pins. Connect one connector to the flexible circuit using a zillion short pieces of wire soldered to it. Dyke the OEM connector off the harness and connect the other Delco connector to the harness. With any luck, that’d actually make it easier to connect up when installing the dash. And you could use three or four small Delco connectors instead of two big ones if you’d prefer, although you need to make sure you don’t mix them up.

That is good advice. The plastic beneath is what broke, but the copper traces and the film got messed up too. I got a replacement unit for $200 off ebay, but it had a different part number. My part is DAC11157 which is used in the 1993. There are other instrument clusters, I think from the 94 and 95, that have a slightly different part number, and although they look identical and accept the same connectors, the wiring is slightly different, and the warning lights are in different locations, so you can plug in the differing part numbers, but they don’t work completely correctly – I know because I purchased a replacement used off of ebay, and learned that the hard way, and the traces on my existing film-printed-circuit-board were in too bad of a a shape to repair-- I spent 2 or 3 hours trying, but to no avail.

On a different note, my XJS has since developed engine problems – it’s very noticeably burning huge amounts of engine coolant – as in steam in the exhaust, steam flowing out from under the bonnet, and engine coolant dripping out of parts of the exhaust. That means that – with a heavy heart – I will be selling or junking my XJS. I just don’t have the funds or the time to keep repairing and refurbishing it.

I don’t believe that there was any secondary damage from the leak, because I shut it down almost right away, and never let it overheat.

I’ve had my cat for 15 years, and will truly miss it. I plan to post to the classifieds, and I plan to let it go dirt cheap if anyone on the forum wants it. So far I’ve gotten one IM from a member in North Carolina who’s interested, so I will reply to him. The car has many good features, but also needs a lot of work – I guess I don’t have to tell the author of “the book”, that these cars require maintenance and repair, and once they get to be 27 years old – like mine – I think that issues will only continue.

Farewell to my XJS convertible. I will truly miss it. Maybe in 3 to 5 years I’ll be in a position to get a new convertible as a toy, but for now I’ll be toy-less, at least in the car dept. :frowning:

  -Phil

Smart move to just get another XJS while they’re still cheap. Not sure I’d wait before buying another… get on Craigslist daily and be opportunistic!

A good home for your car might be with David Boger at everydayxj.com