Disco 1 Auto to manual conversion headaches

Hi all,

I've got myself in a bit of a pickle, having taken my Disco 1 V8 apart over a year ago to convert it from auto to manual. I'm now having a few headaches getting it back together.

I've done most of the work already, but it's all the wiring etc that's now got me stumped...

Obviously some of the wiring is redundant and other stuff needs modifying to suit the new manual set-up, but it would really help to know what came from where in the first place, if anyone can help?

The vehicle is a 1993 Discovery Series 1 3.5 V8i. To complicate matters, it is a Japanese import, which I believe is the same as the UK police spec of the same year. This may be why I'm struggling with the wiring diagrams...

Working along the gearbox loom, the first plug is a round 6 pin plug with 4 wires in use, these are black/orange, green/brown, green and black.
I can't see anything at all that this should connect to. I can only imagine that this is for the combined inhibitor and reversing light switch, but I can't fathom what wires do what and the wiring diagrams don't seem to help...

Next (on a spur) is a 3 pin round plug with 2 wires in use, these are yellow and green.

Based on the wire colours, this would appear to be for the speed sensor, but the plug looks nothing like the one in the Haynes manual diagram. To make matters worse, I don't seem to have a speed sensor to connect it to on the new gearbox and I've already disposed of the old gearbox...

Finally, there are 2 spurs one with blue/black and black and the other with blue/green and black. All on female spade connectors. The former is I think for the diff lock warning light switch, the latter for the transfer box oil temperature switch. Either way, there are only two options, so I should be able to work these out very easily once the battery is back on.

Once the wiring is sorted, I just need to plumb up the clutch and gearbox oil cooler and I think I'll be nearly there...

Any advice with the wiring very much appreciated.

Okay so where do we start.
Well as you have a 200 series V8 disco the Haynes workshop manual is a waste of time re the wiring diagrams, the diagrams shown are predominantly for the 300 series.
If you need to look as wiring diagrams for your vehicle then u need the early 3.5 RR EFI Haynes manual, but as it seems your doing okay so far… perhaps not.

As you correctly say, the auto gearbox reverse light switch is a dual switch therefore incorporates the inhibit starter function for all selector positions other than N & P and being Japanese spec that will possibly incorporate the prevention ignition key removal unless in P, plus the foot on the brake pedal for starting, (if anything like the 20+ years I've had with my Japanese company cars).

So the inhibit wiring will be redundant, leaving u with just the reverse lights to connect into the manual gear box.

The diff warning light, and road speed is taken from the transfer box, manual or auto, and also the box and its temperature sensor, if fitted, as UK spec doesn’t.

That’s about it, out of interest I’ll look at my RR wiring manual and see whats what with the round bullet connector.

Also thats the first time I’ve seen the D1 had a police spec, it didn’t of course here in the UK, it was just a basic model taken from the line, with decals and lights to suit, along with HD rear springs added, what ever the model year.

Thanks for the info discool. I should be able to get my hands on the RR manual, so will give that a try.

One of the chaps in the village also thinks he's got wiring diagrams for various non-UK spec vehicles, so I'll see what he manages to dig out.

Regarding the comment about "police spec" mine is actually the "Camel Trophy Edition" which I have been told by my local Land Rover dealer was the same as the UK police spec of the same year. What I was told is that it's on catalytic converters earlier than the standard UK spec, though I'll freely admit I'm no expert on the different variants that were made, so I may be wrong.

Well after 15 minutes I’ve failed to find in the various diagrams what would have been plugged into the 6 way socket, connectors on there own ant shown, so it’s difficult to find and trace a wire from the colours without an idea or the circuit/s they are used for.
The Haynes RR manual has just a few diagrams covering the various model years.
Anyway if you wish to get a RR manual then there’s a few on eBay. As my photo below, read once just to see what made my RR tick.

By analogy based on the reverse light scheme for the latest version i'd say that the green/brown wire in that 6 pin plug goes to the reverse lights and that's all you need from there on a manual ... use a multimeter and measure for +12V against earth in that connector(might be the green wire), if you find a live bridge it with the green/brown wire and if the reverse lights are coming on then you know to connect that one to the manual gearbox's reverse light switch, the rest of the wires are useless on a manual

discool said:

it’s difficult to find and trace a wire

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You're not joking! If I look at that much longer, I'll be giving up and digging through the garage for some carbs!

sierrafery said:

i'd say that the green/brown wire in that 6 pin plug goes to the reverse lights

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Yes, that would make sense. I'll have a play with a multimeter and a safety pin and see what happens.

sierrafery said:

the rest of the wires are useless on a manual

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Not quite. I think I still need to find and short out the inhibitor switch, so it thinks I'm in park, otherwise it won't start.

cavemanpete said:

Not quite. I think I still need to find and short out the inhibitor switch, so it thinks I'm in park, otherwise it won't start.

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You dont have to dig for that, it's enough to splice in with earth in the stater relay socket's black/orange wire

sierrafery said:

You dont have to dig for that, it's enough to splice in with earth in the stater relay socket's black/orange wire

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Of course that modification is also a well known method to bypass the D1s immobiliser function associated with starting the engine, so that function will now be removed from the vehicles security system, if a system is fitted to the OPs vehicle that is.

I did the same with my Japanese import last year I removed the auto and fitted a manual from a do not v8 I bought, I fitted the donor transfer box as well. I simply used the gearbox loom that came with the donor vehicle it plugged straight in to the main loom. I swapped the ignition switch over as well so I did away with the interlock, the plug was different on the main loom for the ignition switch so I deppined them and used the plug from the auto on the manual ignition switch. I had to swap the relay for the cruise controller for the donor manual one and everything works fine.

sierrafery said:

You dont have to dig for that, it's enough to splice in with earth in the stater relay socket's black/orange wire

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Black and orange connected to earth and she's started straight up, so thanks for the tip. Not sure my neighbours will be so thankful though as the exhaust is still off, so running on manifolds