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I've broken my speedo - but not sure how?


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2005Td5 D90.

Earlier I was fitting cruise control with a SpeedoHealer as described by V8Freak here. In order to fit the cruise I have added some connectors in the ECU black plug, and to make the SpeedoHealer work I have interrupted pin 13 where it enters the ECU and connected the SpeedoHealer in series - as per the directions.

Now my speedo does not work (and nor does CC). :(

As I understand it, the speedo is fed from the speed transducer (which also gets a live and earth connection) in the back of the transfer box and the speedo then sends a signal, via pin 13, to the ECU. So I should not have upset anything, right? Well, something is obviously wrong. Do the wires to the speedo pass through the driver side seat box and could I therefor have upset them? Have I fried the speedo working on it live? ..I know, I know. Is there a fuse I should be checking?

Any help much appreciated.

Chris

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My Range Rover Classic speedo is electronic and has not worked for years, and years before I bought the car. I have changed everything, speedo, cable, tranducer, some resistor or something, and had Land Rover connect the car up to their computer, they said the speedo was not working but not why it was not working. (And, they wanted £120.00 to tell me that, an hours labour for a 3 min job. I ended up given £20.00 to the bosses chosen charity.) I think it's the management computer. My sat-nav has a good speedo though.

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I think I will start by checking the obvious first - power and earth to the pickup and continuity to the back of the speedo. I can also bypass the SpeedoHealer just to eliminate that...

Cheers

Chris

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Good news! The very first item I tested was the fault. I tried to establish that the speedo sensor had an earth; it did not. I could not establish what has happened to its earth - anyone know where it earths, the cables disappear into the loom? I ran a new earth and the speedo now works again, and I can cruise in fifth. Hurrah.

Cheers

Chris

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Good news! The very first item I tested was the fault. I tried to establish that the speedo sensor had an earth; it did not. I could not establish what has happened to its earth - anyone know where it earths, the cables disappear into the loom? I ran a new earth and the speedo now works again, and I can cruise in fifth. Hurrah.

Cheers

Chris

The speedo transducer's earth goes back to a splice joint in the engine harness (this splice joint is shared with several other devices on the engine harness), from there it runs back to the main harness via the engine harness/main harness connectors C0162/C0448

In the main harness, it runs down to a Blue 20-way header (C0287) in the locker under the driver's seat, and from there it runs back to the main earth header (C0550) which is mounted to a stud on the bulkhead in the engine compartment.

.

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Thanks PaulMc! Just too late to have helped me, but you have mentioned the problem area.

Once the speedo was fixed and the CC working, I went for a short run up the dual carriageway to try out the CC. The engine seemed rather flat - which I had noticed before and put down to the ECU not getting a reading from the speedo and assuming that the car was stationary. I got back and connected the computer which showed a number of odd faults relating to driver demand problems, ambient pressure circuit, and open loads on MIL lamp and on glow plug lamp and glow plug relay. I checked the engine inputs and lo, the MAF sensor was reading '4', it's default knackered status. Since the MAF is only about three weeks old I smelled a rat and went in search of it. Looking for the MAF wire colours in the driver seat box in search of a displaced pin. My wife identified one of them as going to a 'blue connector' in the seat box - a connector with no connections.

Now I started putting 2 and 2 together.

When looking for an ignition switched live under the seat I had found a handy blue connector which I assumed was for the ABS ECU (which I do not have, having a basic truck). I had removed and discarded the little blue plastic protective cover and inserted a correctly sized pin to get the live I needed for the SpeedoHealer - I subsequently used a different feed for the SpeedoHealer and removed the pin.

Now 2 and 2 were at about 3.9...

I went over the road to SimonR's and borrowed the little blue plastic cover from his 110. I looked inside it and what do you know? Lots of little connections in two neat rows - there was more to this than a mere blank! 2+2=4. Fitted Si's connector in my 90 and the AFM immediately read 57Kg/Hr at idle.

Since I have access to the correct pins for the blue plug, I went to make up an ad-hoc replacement for the connector cap and found the original one, still in the dustpan where I had failed to throw it in the bag of rubbish I took to the tip this morning. Born lucky. :) The speedo now works with the sender on it's original earth, and normal performance is restored.

Thanks due on no small part to V8 Freak for his many iMessages of assistance and brainstorming and to SimonR for allowing me to cannibalise his 110! ...and of course, my wife, who I take too much for granted!

Cheers

Chris

(feeling silly)

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