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Defender instrument electrics

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Evenin' all,

About a year ago the wipers in The Beige One tied themselves in knots, the end result being that the instrument panel and dash had to come out. The wipers now work very nicely thank you (touch wood), but the instrument electrics have been behaving strangely ever since and sorting it out has now risen to the top of my to-do list.

Also, while the instrument panel was out, I did have a fettle and remove all of the standard incandescent bulbs and replace them with LEDs and a controlling dimmer circuit. This meant cutting out all of the wiring associated with these bulbs, so it's possible I've disconnected something I shouldn't have. Trouble is, I have no idea what.

For starters, I'm going to ask if anyone has a decent wiring diagram for a 1995, 300tdi, rhd 110 Defender? No air con, no ECU, no alarm, no immobiliser.

I have the workshop manual, but the section for electrics (86 if I remember correctly) only has diagrams for the alarm and immobiliser circuits. Trawls of t'internet have yielded all manner of suspicious doodles and searches on this forum have usually ended up in dead links. And I doubt my search terms have helped to be honest, but if someone could point me towards a decent diagram, I would be most grateful.

And now the symptoms:

With the ignition in stage two, the red lights which illuminate vary each time. Sometimes it's the battery only light, other times it'll be battery and the "( ! )" brake warning, occasionally "(P)" comes on too, but usually not until it's been for a drive. The oil pressure warning only comes on occasionally.

Once the engine's started, the warning lights work as expected, although I can never really be sure about the oil pressure light . . .

Then there's the fuel gauge. It always reads full, but it's not perpetually shorted. With the gauge removed, I took resistance measurements at the green and green/black terminals at regular intervals (electrics off) and this shows that the sender resistance varies between 16 Ohms when it's just been filled to 170 Ohms when it's done about 350 miles (I get just a shade over 30mpg at the moment).

This graph shows the sender resistance against miles covered since last fill up.


I've tried two gauges, but each one shows full when it's attached. Out of curiosity, I put the one of the gauges in line with different resistors and found it reads full at or around 100 Ohms and empty at about 1000 Ohms. Attached is another graph that shows by-eye estimate of indicated level against circuit resistance


Since one of these items it out of scale with the other by a factor of ten, my usual assumption would be that one of them is up the knack, but because everything worked fine until I removed the dash, I'm inclined to think that something isn't connected which should be, or vice-versa.

So there we have it, anyone got any suggestions of where I might start looking please?

And I'd also be grateful if anyone could tell me what the expected working range of the gauge/sender should be too please.

Many thanks in advance,


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That's brilliant, thanks Western. Blummin' lifesaver :)

Cackshifter; no, it was just the illumination bulbs that go in the gauges which I replaced, the warning bulbs are still the usual filament type. I've checked each lamp by putting voltage at the edge connector, so I know the circuit's good from the tracks to the bulbs.

It's quite possible something's been displaced, cracked, broken, disturbed and/or upset when everything was dismantled of course . . .

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the warning light panel plugs should click into place, the engine loom maybe old & the wire outer covering get brittle & splits as the oil pressure wiring sees amore than it's share of heat from the engine,

the gauge illumination is the red/white trace wires & the earth for each gauge is plain black which is daisy chained to each gauge then to a large 4 or 6 way bullet connector.

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  • 1 month later...

Well, it looks like I've solved the fuel gauge issue:

It would appear that the green plastic bulb-holder bowl also secures a very fine wire to the metal chassis of the gauge. This is then provided with ground via the long threaded rod on the back. If there is no ground provided by this terminal, the gauge steadily rises to full. By soldering the exceptionally fine wire to the metal case where the green light bowl would normally live, everything returns to normal.

So that's one thing sorted ^_^

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