Disco 1 transducer (speedo) quick question

Hi guys i've bitten the bullet and ordered a new transducer for the disco, done a little looking about on here and about on google.
I know its a 6mm hex bolt (if it hasnt been changed) and im assuming a 1 or 2 cable plug

Now my question.

Whats the chances of that bolt snapping when im trying to remove it, is there anything i should be watching for?

all tips and advice welcomed

Possible, although its position is quite protected it all depends where you vehicle has been in its life, if in doubt give the screw a splash of PlusGas befor u start.

OK i have a new update and its not good i changed the transducer today the old one wasn't rounded but it did come out in 2 parts.
got it all back together and it was looking good it fixed it, until tonight now as soon as i pull off the speedo jumps to anything from 20 to 30mph then it will go up to about 45 and it wont change from that no matter how fast or slow i go until i almost stop then it will drop back down!
any suggestions guys and girls i need a working speedo and its looking like the £56 i just spent on a transducer wasn't the fix.

ceffyn said:

any suggestions guys and girls i need a working speedo and its looking like the £56 i just spent on a transducer wasn't the fix.

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When I first read your post I thought of the regular speedo failures in my '98D1 Disco, what I have found was that it is only a bad connection of the plug onto the transducer on the output of the gearbox, mine goes on strike about once per year and all I have had to do was pull the plug off the transducer scrape the contacts and then replace the plug, it's good for another year, whilst the contacts are dirty the speedo jumps and jives all over the dial, this of course may not be your problem but it works on mine. Check also the condition of the wires to the plug.

just been out removed the plug on the transducer and sure enough it needed a clean, cleaned it all up and still no change i payed a little more attention this time so have some more info hopefully someone will have an idea.

pull off in 1st barley touching the pedal at 1k rpm my speedo is at 30 already if i accel it will go up to 45ish and stay there i have to slow down to tick over speed in 1st to get it to drop again after its gone up

any help on where or how to test what would be great i travel a lot and need to know my speed

ceffyn said:

just been out removed the plug on the transducer and sure enough it needed a clean, cleaned it all up and still no change i payed a little more attention this time so have some more info hopefully someone will have an idea.

pull off in 1st barley touching the pedal at 1k rpm my speedo is at 30 already if i accel it will go up to 45ish and stay there i have to slow down to tick over speed in 1st to get it to drop again after its gone up

any help on where or how to test what would be great i travel a lot and need to know my speed

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It maybe more a case of how the signals are being interpreted than the signals themselves.

Don't worry about your speed just go with the flow, says one that never looks at the dash display, but it's has been mentioned before that the electrical connection can sometimes play up, but then after a clean and reconnected it's back to normal.

i go with the flow until i see a speed camera then i get close to brown trousers waiting for a flash haha, anyway that aside the transducer is new fitted yesterday (new new not new 2nd hand lol). and i have now cleaned up all the plug and connections going into it (im no pro cant say im 100% its good enough but it looks clean and contacts are shiny)

where else should i be looking. what wires on the back of the clocks correspond to the speedo and can i check for voltages!
are there any other connectors in the link between the transfer box and the clocks!

Mrs aint too happy with no speedo now and me spending money on bits that aren't helping lol
as always all advice is welcomed

Edit: Speedo randomly started working correctly tonight for about 3 or 4 minutes then went back to being all crazy and high. is there anyone who knows where the wiring runs and what the wire ratings are im thinking it could be a split/melted/bare wire somewhere earthing out so im willing to change all the cables just need to know where they go and what gauge cable i should use.

Bump: still need help on where the wires run guys i cant see where they are going from the transducer and need to try replace them asap to rule them out as the problem.

ceffyn said:

Bump: still need help on where the wires run guys i cant see where they are going from the transducer and need to try replace them asap to rule them out as the problem.

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The wiring from the transducer runs along the top of the gearbox into the engine bay iirc. Along with the reverse light switch wiring and the wire(s) for the diff lock warning light.

The reverse light switch wiring on mine managed to wear through and short out on top of the gearbox which caused numerous problems with electrics.

Hope this helps.

robbh said:

The wiring from the transducer runs along the top of the gearbox into the engine bay iirc. Along with the reverse light switch wiring and the wire(s) for the diff lock warning light.

The reverse light switch wiring on mine managed to wear through and short out on top of the gearbox which caused numerous problems with electrics.

Hope this helps.

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it sort of helps i know where to start trying to look now however when i said where they go i meant when they come from the transducer what's next on the circuit.
umm best way i can try explain it is for example the red/black wire thats on the transducer plug i "think" i have found on the rear of the clocks. however i dont know if it just go's from A the plug to B the rear of the clocks or if it makes a stop off at C (fusebox, ecu,module) on the way.and like wise for the other cable light and dark green i think it was but i have no clue where that one is going.

the transducers are usually the issue, if you dont want to buy a new one get a used one

Given you have fitted a new transducer, and cleaned the socket connectors, check the wiring as mentioned in post #10 - quite a bit of room under there, next to the R380 - be grateful its not an auto - cos then its all a bit tight

get some vaseline in the connector onto the transducer too - will stop it oxidising, or worse...

the cables are in plastic trunking, and can rub on just about anything....


I would then be looking at the connectors onto the PCB of the instrument cluster... I've seen these grow verdigris, usually when there is some moisture about from leaks, off roading etc....

Disco1BFG said:

Given you have fitted a new transducer, and cleaned the socket connectors, check the wiring as mentioned in post #10 - quite a bit of room under there, next to the R380 - be grateful its not an auto - cos then its all a bit tight

get some vaseline in the connector onto the transducer too - will stop it oxidising, or worse...

the cables are in plastic trunking, and can rub on just about anything....


I would then be looking at the connectors onto the PCB of the instrument cluster... I've seen these grow verdigris, usually when there is some moisture about from leaks, off roading etc....

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already checked and cleaned the connections on the back of the clocks and i was trying to find out where the wire run too so i could just cut out and replace the wires saving me the time of trying to get up over the R380 to find them.
will vaseline the connector shortly though to see if it helps in the mean time.

As already stated the wiring from the transducer joins other wires to form a loom, then joining other wires to form a loaner loom will will appeared behind the fusebox where it splits with the transducer wiring along with others to go to the rear of the speedo pod.
So no hope in finding the wiring involved unless you dismantle the looms.

If u believe there's an issue with the wiring, get the meter out and test continuity of the wires between the transducer and the dash pod connector, I will be a lot easier and if u find one that's faulty replace it.

Vaseline will not improve connectivity only prevent any future issues due to dampness within the connection.

discool said:

As already stated the wiring from the transducer joins other wires to form a loom, then joining other wires to form a loaner loom will will appeared behind the fusebox where it splits with the transducer wiring along with others to go to the rear of the speedo pod.
So no hope in finding the wiring involved unless you dismantle the looms.

If u believe there's an issue with the wiring, get the meter out and test continuity of the wires between the transducer and the dash pod connector, I will be a lot easier and if u find one that's faulty replace it.

Vaseline will not improve connectivity only prevent any future issues due to dampness within the connection.

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yeah i knew it wouldnt help connection but it will help slow/stop more corrosion until i can get a new plug
and the problem i've been having mainly with checking the cables is my lack of knowledge on the transducer. i've found some places saying its pulse and it runs on a + and earth and other places saying its pulse creating its own AC current. i did do a little testing when i had the clocks out and found the black/red wire i think it was put a multi meter on it and tested for dc voltage using an earth. now this is where i got confused more. that was before i read about the possibility of it being AC and i was getting random results ranging from 7v to 11v while on the move, had tester where the clocks should be and phone in a holder just next to it with GPS speedo. but not at any point did i get a 0v reading unless i turned off the engine.
im away again tomorrow working at a motocross event but Tuesday i'll have another go at the voltage thing and see if i can get a video of it.

the reason i think wire or plug.
give the plug a good clean and the wires a little pull/push to move them about. the speedo now randomly reads correct below 30, sometimes will continue to work with some bounce up to about 50 then it sticks until i hit about 70 and the dial jumps back up to where it should be. i did notice on the way home tonight that it didn't want to go up passed about 76 but that could have been discrepancy's between the dials and GPS speedo (took the tank to 85 on the flat just to see how she felt sounded stayed up there 2 or 3 mins dropped back to 60 lol)

and yes i have a good GPS speedo in a very convenient place that i now ALWAYS have on to be safe lol

Edit: as for the wires go into the look that i understood instantly but i was trying to see if anyone knew where they came out of the loom. for example when it go's into the loom is does it keep its color all the way to the other end and if so where.

different circuit but its only way i can think to explain better

say the rear window that go's motor - loom - switches - lift module - fusebox (before im corrected i know that could and prob is wrong)
what i would then want to do is go motor - single switch (on/off) - fuse - switch power (yes i know that would only make it go up or down and not both but you can see what i mean

if the only option is to open the loom and look for myself then so be it but no harm in asking if someone knows how/where they run

also thanks for the help so far and any other help you guys have been great and patient with me most would have told me to F*** Off by now hehe

What ever the condition the transducer gives I don't know I'm not interested but I suspect is a variable voltage.
So forget voltage or any thing else, check the continuity of the wiring to the speedo head, if it find a break then etc etc. Not to confuse the issue but thats assuming the transducer to speedo is a direct feed as vehicle speed is also used for engine management on some disco's. The wiring diagram in a Haynes manual hopefully will clarify what's what for your vehicle.

i have been assuming the umm speed cable i guess its is would be 1 part hence the thought of changing it, if i get some time on the track tomorrow i'll see if i can get to it in order to do a continuity check. i have a quick question on that though hehe

i know test from 1 end to the other and see if it makes a connection, but my theory is its earthing out thought a for argument sake side split letting copper touch metal of some sort not actually a broken cable.
would it be worth testing from each end to a good earth point and having a wiggle to see if i can get anything up on the meter?

additionally if i find a earth problem would i do any damage if i was to cut and replace the speed cable as a single if its meant to go somewhere else on the loop?

ceffyn said:

would it be worth testing from each end to a good earth point and having a wiggle to see if i can get anything up on the meter?

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Yep, sure would - this is likely the problem. Probably best done on a continuity buzzer setting - and waggle until it beeps!

ceffyn said:

additionally if i find a earth problem would i do any damage if i was to cut and replace the speed cable as a single if its meant to go somewhere else on the loop?

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Don't know* - but IMHO,you are making unnecessary work there - just insulate any damaged bits, and see if it works - if it does, then just use it....

* I don't know cos I don't know if the cruise control or EDC (etc.) - if fitted use the signal.

I know it's a beand new transducer but is it genuine etc. And how do you know it's in 100% working condition. If it's ok I suggest it's a bad earth or a part broken wire giving a weak signal.do you know a mate or anyone who is a auto electrician mate. You could be buggering around for weeks.
Good luck,