I have seem them used interchangably.

My speedo is erratic...I have cleaned the tangs/connections behind the gauge cluster.

It is at the shop and they said they can't order the part, that I will need to provide for them to install. if they are different parts, should I order both and have them install both?

Where is the best place to purchase? Can some1 provide a link to these part(s)?

For a 90 XJS Base Vert.

Thanks....Karl

 

No, the transducer is used on earlier cars ( and sedans) and goes on the transmission tailshaft. It's gear driven and produces the pulsed speed signal to the speedometer. The later cars ( post 1983 I think, but I'm not certain) switched to a differential mounted speed sensor. There is a toothed wheel inside the differential and this is sensed by the speed sensor that is mounted on the rear differential cover. There is also a speedometer interface that converts the signal to a usable form for the speedo and trip computer.

As a test, I'd switch your trip computer to the instant fuel economy and see if it is giving readings when the speedometer goes erratic. If the trip computer stays running fine when the speedometer goes erratic, then it's on the instrument cluster side, probably a ground. If it also fails when the speedo fails, then it's on the signal side somewhere. Here is the diagram for an 89, which should be the same.

Looks like the diff mounted sensor is no longer available from Jaguar.

 

Before replacing the VR sensor I would clean the connectors in the boot.

There a speed interface unit on the LHS. it is up in the buttress on a coupe not sure about a ragtop. There are 2 connectors, one goes to the sensor in the diff and the other goes to the instruments.

 

Is this what I need?

https://www.ebay.com/itm/Speedometer...sAAOSw1-5bIC-N

 

No, that's a speedometer transducer.

You need part number DBC2632, pic below


Cheers
DD

 

Just to clarify, it was about 1983-ish that the change from cable-drive speedometers to electric speedometers was made.

The change from the transmission mounted speedometer transducer to the differential mounted speed sensor was at VIN 142xxx or 144xxx....something like that. This was early/mid 1987 calendar year. (My XJS was 139xxx and built Feb 1987)

Cheers
DD

 

Where do I purchase?

 

Hi Karl

David Manners can get them £102 inc Vat + Delivery

David Manners Jaguar

 

Google "Jaguar DBC2632"; there are likely many vendors selling it.

Cheers
DD

 

OK - changed my rear discs and overhauled the brakes and put everything back. Installed the sensor with the same fitment and drove off. Hurrah the brakes work superbly but no speedo and no distance being recorded on the trip computer. Pulled the sensor and the end is broken off. Looking at the shoulder of the boss of the plastic sensor it looks like it has distorted over time and so allowed the sensor to move in further. 30 years old this year, so distortion of the plastic can be expected in a hot aggressive environment.

Warning to us all - measure the gap prior to putting the cage back up. I am now in the position of buying a new sensor and 10 shims and trying to fix it with the cage in place.

No chance getting anything perpendicular onto the crown wheel and matched to the shoulder of the casting of the dif cover so I am going to start with 10 shims and a lump of plasticine. I will post up how I get on. I have the rear of the car up on axle stands under the two rear jacking points so I can run the engine in drive. So I aim to reduce the shims until I am at 0.020 - 0.040" (this is wrong - see later) and then check speedo and trip work.

For information, the change point from the tranmission mounted sensor was 144262. The sensor is three lead so it most likely has a power and earth and signal wire. The power is unlikely to be battery voltage but rather a stabilised 5V. The lead goes up to a signal amplifier which, on the convertible, is behind the panel that the LH boot strut attaches too. From there the signal goes to both the speedo and cruise control. In testing and tracking I removed that panel but it looks like there is just enough lead for one to disconnect the sensor lead from the fly lead to the amplifier, once the carpet has been removed from that panel.

In hindsight the best option for dropping the cage, to do the brakes, would be to remove the carpet from the panel to which the LH boot strut attaches. Feel behind and then disconnect the sensor lead from the fly lead for the amplifier and then prise out the grommet in the left hand front boot wall so that the sensor connector might pass through then lower the cage complete with the long sensor lead on. Then don't touch it whilst overhauling the brakes ! If I did that I would not be £110 out of pocket - and a lot of hours better off !

I had looked for the terminal block for the sensor as I started to lower the cage and it became evident the block was somewhere inside the boot. I removed the spare wheel and followed the lead up to the panel but faced with "remove the panel and boot strut v undo two bolts and pull the plastic sensor out, I opted for the latter with the attitude - "what could possibly go wrong?"

[Anyway pleased with my disc change and calliper overhaul - new pistons and seals on one and the other was a new calliper two years ago so ok. I also now have the handbrake working the best it ever has. The handbrake callipers must have each been on and off about 6 times before I was content that the arms each side both shifted the pads just clear of the discs, under the opperation of that plate with the hooks that go into the arms. That just is not possible to verify with the cage in position on the car.]

OK I was then going to ask had anyone got a technical release bulletin with Jaguar's definitive version of the air gap as certainly today, when I gave over 15 minutes to the job in the OE workshop manual, I could not find anything. For the engine speed sensor on the starter ring teeth they want 8 to 32 thou. And that seems smaller than what you guys are suggesting. But before I signed off on this long post I decided to look again, begining to end. And sure enough, not in a transmission section, cruise control or suspension but in "Instruments 92 model year on" (Well just why would I not look there for my 89 model year electrics !) there it is. Chapter 17, fig 17 shim to 0.010" to 0.020" Loving it. Final instruction for "seed sensor renew" "Close the boot."

So now we have Jaguar's own data 10 to 20 thou. Therefore 15 thou distortion of the plastic would have been enough to get the tip of the sensor on my car being belted by the crown wheel and coming off a very poor second best.

 

If the tip of the senor is floating around in the diff, I would drop the cage again and pull the rear cover and clean out any metal and/or plastic that is floating around. Don't want to rebuilding the diff. While you have it out it's eay to set the gap. I used Plasticine on the sensor to measure the gap.