I took my cluster out because these three gauges weren’t working and cleaned up all the ground contacts on the board and have even gone as far as running another ground wire to the cluster but it still won’t work like it’s supposed to.

The pin on the harness that supplies ground for the cluster reads too high on resistance in order for to be working properly and despite my best efforts to correct the problem, it still persists.

The last thing I can think of to try is to get a different nut and bolt for the extra ground wire and put it on the metal grounding strip behind the cluster as opposed to putting the wire under the screw that doesn’t ground out the circuit board.

If anyone has any ideas as to why it still won’t work on the three gauges please let me know as I’ve been trying to fix this for a month now with no major breakthroughs.

The green underline is where the new ground would be put in with a nut and bolt as I’ve previously tried the slot next to it with the screw that doesn’t hold down a board strap and that has not worked

 

Model year and engine?

 

Since that PCB looks like the early Barrel Gauge nightmare, have a read of my fix from some 35 years ago.

Good luck.

 

1986 V12

 

The only issue with this is that I’ve done this already minus the extra washers with no results yet. But I will try cleaning everything again today and follow up with results.

 

In order to verify if the earth that is run through the ribbon cable is the problem, have you tried just running a completely separate earth wire from one of teh gauges to an independent earth point and see if there is an improvement?

Good luck

Paul

 

Still no luck after cleaning everything up and hooking it back to the car so now I’m not sure what else to try besides throwing it in the garbage and buying a new one

Update: I took the cluster from a second 85 XJS I have and put it in the car and it still will only read the battery gauge when I know that at least the oil and battery gauge work on this cluster. Now the fun begins of trying to locate all the different things that could be wrong in the car

 

The next thing I would do is to carefully check each copper track from the multiplug to the individual instrument, and to do the same with the earth (or return) track from the instrument. Look particularly carefully at multiplug/copper track connections.
Also wurth reading the section of the Great Palm's book on the instruments. The electrical connection to the individual instruments is unbelievably flimsy and just cleaning up the various tiny scews and bits between the instrument, inside the instrument, and the track can do it.
Also with a meter check that a signal is setting to the multiplug. The attached may help

 

I feel like my last update was confusing and so I’d like to clarify that I took a different working cluster out of another jag that I have (at least the oil pressure gauge worked from what I noticed) and it did not work when put into the car I’m having trouble with and so I’m leaning more towards a wiring issue with that car somewhere but don’t even know where to begin to start. But I imagine the pins will give a general idea of where. I’m just worried it might warrant replacing the pin connectors themselves too which may be a job beyond my expertise.

I also haven’t been able to find what the pin voltage should be reading from the connectors so if anyone knows before I find it on my own it’d be much appreciated.

 

12V would be the spec I would think, although I have never tested that at the binnacle.

Start at the beginning:

1) Solid WHITE wire from the Ign Switch MUST have battery voltage when in the ON position. I have had a few with much less, and lots of weird events took place. The electrical section of that switch is WELL documented as reeking havoc now due to age and 30++ year old British grease.
2) Follow the loom from the Ign switch AND the binnacle, find any loom connectors down the line. Separate them, clean the male/female pins, and then continue to the Bulkhead connector. NOW, you are up there and the steering wheel etc is on the other side, so I suspect the Bulkhead connector that is alongside our, RHD, accelerator pedal, is on the LH side on yours, pure guess on my part. These Bulkhead connectors will need cleaning now due to age again.
3), Straw clutching here, but what the hell, check the main engine earth strap fiasco around the B Bank engine mount. Check the main earth pins alongside the battery, the earth straps on the radiator panel, and the few that MAY be on the Inlet Manifold near the 5A tract (some markets have them, some dont), you may be getting a feed back from a bad earth, it happens, usually the gearlever gets real hot, but not always.

 

Forgive my lack of knowledge on the ignition switch, but would it be possible for everything else to work powered by that switch except for the three gauges? Or would everything else not work if it was bad? And I know the battery gauge only works because it’s a direct feed but it still confuses me that the other three barrels show no signs of life no matter what I try.

As for the rest of the advice I’ll check it all out and see what I can find. It is much appreciated.

 

I agrtee, but it is a Jaguar, and Lucas electrics, so anything is possible.

I have chased many of these types of issues since the MK7 days, and even though I sorted them, I took no real note of how or why, what youngun does in reality.

My XJS's gave little trouble, but the binnacle earth was an issue on all of them.

The Ign Feed to the binnacle would be my best guess. I doubt that battery barrel is live fed, as when the key is in your pocket, that gauge be "dead".

My one eye now means reading wiring diagrams is not possible, BUT, these systems are simple, frustrating, annoying, but simple when a logical diagnosis pattern is followed.

If I read it correct, there is an issue with the Ign Feed to the binnacle. Probing the multi plugs, unplugged from the PCB, with the Ign ON, write the colours down, probe again with the Ign OFF, write it down, compare. That will establish which wires are Ign Live. Trace them via the PCB connector to where they go, looking for a "missing link".

This will take time obviously, but id dimplr yo do.

If one of my kids turns up, I will get them to read the wiring diagram, and post back if still needed.

I need a beer, that took some serious brain power to type without mistakes, HA.

 

I tested the pin connectors again to make sure I didn’t miss anything and I tested the ground pin on the smaller clip which read 1.1 ohms. I know enough electrical to know that’s not good. That said I have my own wire in there attached to the ground point under the dash that reads at .1 ohms itself. Now I’m not sure why this remedy wouldn’t solve the issue but anyways.

It was also interesting to find that there was very minimal voltage at the gauge pins, about .34 bolts or something similar of the sort but it would read 12 just fine in other places like the lights which was expected as all the lights work just fine. Although, this could just be the result of the car being off, and only the accessories being turned on? Most likely I think but I could be wrong, I’m new to this sort of stuff, usually more of taking things apart and putting them back together, not chasing wires. The Speedo and Tach pins both read at 12 volts as well.

I’m thinking that I have to chase down the ground wire from the connector and find where it is grounded to and clean it all up I just don’t know where that might be. And looking at the wiring diagram is confusing but I’m determined to figure it out.

Testing further with the ignition module will come this weekend when I have more time to devote towards the project but for now these are my findings.

 

You might find this useful. This is a mod I made to a diagram I got somewhere. I corrected the turn signal connections. I also revised the pin numbering to match the connectors on the wiring harness. Note that there are two ground connection, one on each connector. Hope it helps.

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Appreciate the response. Upon further inspection with the car, I realized I kept forgetting to turn the lights on while working with the dash. It works but the magnets are a little messed up, I’ll clean it and get back with results
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have you tested the sensors for each gauge to make sure they are working?

 

I use one of the nuts for my ground.

 

When testing resistance to ground, your meter reading can be thrown way off if the battery is connected. To get an accurate resistance reading, disconnect the battery first. I prefer to test the ground by applying a load, such as a headlight bulb, and test for excess voltage drop.