Speedometer gauge intermittently dropping: Please help me fix my Speedo!
 

Gday guys

I'm hoping you might be able to point me in the right direction.

For the past week or so, my analoge speedo would occasionally drop and not register at all. I would give it a hard little tap on the outside plastic and it would pick back up again and start working.

Today i noticed it happening a bit more frequently so I was wanting to know if you think maybe I have a loose wire or similar?

Can it be a relatively easy fix? The reason I ask is I have a busy week ahead and i am due to go back out to sea for a month next Tuesday. :icon_boat:

If shes too involved I might have to wait until I get back home.

Any idea on where I could start?

As always your guys input is most appreciated :icon_user:

Wonky operation of any of the meters is often traced back to dirty/corroded connections on the circuit board on the backside of the instrument cluster. It's fairly simple to remove the cluster and clean the contacts and connections....and add a redundant ground wire as well.

Post back for more details, if needed

Cheers
DD

Cheer thanks Doug

So there is a circuit board on these Pre-Marelli XJS (mines an 85) for the instruments?

Where do I begin in getting the instrument cluster panel off and getting access to that board?

Thanks in advance :)

Yes




It's been a few years but someone will come along and fill in anything I've forgotten.

First remove the trim pieces at the perimeter of the cluster lens. You'll see the screws left and right, and one screw for the joiner piece at the top.

Now remove the blank-off plugs at each upper corner of the cluster which reveals the two screws that actually hold the cluster in place. Remove those screws, wriggle (gently) the cluster outward a bit. Reach behind to release the two wiring connecters (press-the-tab type of thing) and then remove cluster from car.

Unplugging the wiring connectors gets tricky as, usually, there isn't much slack in the harness and therefore not much room to get your hand back there.

When removing the cluster be careful to avoid snagging the printed circuit on a sharp edges or such.

Removing the steering wheel makes the task a bit more pleasant but is an extra step and not essential by any means.

Cheers
DD

When mine started doing that and then proceeded to get worse it was the transducer on the transmission. Not saying yours isn't the circuit board, I'm just saying mine was doing the same thing then it finally quit. Changed out the drive on the tranny and alls been right for well over 4 years now.

Happens. Could be Transducer or gear needs to be rebuilt. Happened to me. Changed both. Rebuild is what I needed

Thanks for the feedback guys.

Doug, thanks also for the steps :)

So the transducer...how do I locate it to run my eyeballs over it?

Looks like two areas i might have to look at

Hi Bud

This should help you find it, if you need to buy a new one its about £70 (UK)

Don't put it off any longer Bud, buy that heavy duty 3 ton Jack to-day!

1995 Jaguar XJS: Electrical Problem 1995 Jaguar XJS 4 Cyl Two ...

JAGUAR SPEEDOMETER TRANSDUCER 82-88 XJS XJ12 DAC4569 | eBay

Thanks OB. i appreciate it mate.

i am running out of time so it might be a "return to shore" project next month now, as she isnt a show stopper.

watch this space...

Hi Bud

Why not have a look round a Jag breakers, you might find a SH one for a few dollars, then at least you could give that a try before you take any instruments out. 'even if you don't fit it before you get back'

Who knows you might even pick up a nice Set of Lattice Alloys while you are there.

Hang in there Bro and don't get down, it happens to all of us including me but that's all part and parcel of owning an XJS.

Left side of transmission, more towards the rear than the front, two wires.




The transducer is another known problem area, yes, but the fact that your speedo responds to being tapped more strongly suggests a problem at the instrument cluster.

Cheers
DD

Hi Bud

Just had a thought!

You could try disconnecting the push together electrical connector of the Transducer and giving the connector plug a good clean.

Its probably well corroded after all this time and as such not responding as well as it should.

If you are going to pull the cluster out then that would be a good time to change all the bulbs or upgrade to LEDs.

Guys thanks so much for the feedback. This is why this forum is the great place that it is! :)

I am running out of time now so might come back to this thread after I get back from sea.

Guys, it only just occurred to me also that the problem HAS to be behind the dash, as I give the cover a few whacks with my knuckles whilst driving and it comes alive again. So I think, luckily for me, that it might be a loose connection behind there.

to be continued.....

Finally I started this
 

Heh guys

Sorry it took so long to get back to this. Been busy with work and stuff.

So I took out the instrument panel today.

No major dramas. Firstly I hit my cut off switch in case i short anything out, then, thanks to the advice of you guys I took the necessary screws out and removed the panel out. It had two main connectors going to the back of the panel and also an earth wire which goes back to the chassis. (So I guess I don't need to add the redundant earth wire?) I noticed it is one main circuit board membrane overlaying the plastic housing. Pretty bizzare but then again I haven't ripped out too many instrument panels in my time, especially in a XJS.

So I noticed after removal that everything seemed fine. The copper tabs on the membrane looked real good for a car of its age, and both connector harnesses had nice shiny copper pins.

Nevertheless i cleaned them up still with some Electronic Circuit Board cleaner I had lying around.

I thought maybe the harness wasn't seated in real well as one of them was easy to come out. So, without finding anything major I tightened up all connections and put back in the dash and went for a test drive.

Unfortunately it didnt get it! I had to tap on the dash again for my speedo to come up, however I must of awakened something as it is working more frequently now.

So I guess next is to take instrument panel/cluster out again and this time pull it apart and get to the actual speedometer instrument and see whats going on there.

Stay tuned....

You won't be needing that speedometer Sunday anyway, if I am disappearing in your mirrors you are doing well over the speed limit.

ha ha ha ha ha.....I usually just follow other cars to get a pace when my speedo chucks in anyways :)

Good plan. There is a good chance that the connections to the speedo head itself are not quite sound, or that you will see something a bit loose once it is out. However, it might be an internal thing inside the head. If after cleaning etc it still is a problem, a second hand speedo from a breaker is cheap and plentiful. Loads in the UK.

Also, while it is all apart, you can renew the instrument bulbs with 5 Watt push fits in place of the OEM 2 or 3 Watt ones, and remove the little green bulb covers inside the cluster that will be black with age and chuck them out. Transforms the instrument lighting.

Greg

Hi Greg

Great idea about the 5 Watt bulb swap as the instrument lighting seems to leave a lot to be desired.

I know that this might cause you to bang your head on the Table! in an Oh No! sort of way but what are your thoughts on swapping those bulbs for 'Blue Led's ?'

They always let one in with the humans.