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hi can anyone help

ive got a 3.9 efi with a bw t/case fitted into a 1987 90.

ive wired up the ecu and got the engine working ok

i then wired up a td5 dash and got all the warning lights and the fuel and temp gauges working ok

the speedo lights up but not showing any speed

the speed transducer is conected to the speedo and the ecu.

yellow on the transducer and black red on the speedo via the ecu

ive tested the voltage at the speedo and it goes from 12v to 6v about 6 times when i turn the wheel.

question. is the rrc speed transducer suitable for the td5 dash. ie the output from the transducer or have i got a faulty speedo

thanks tazza

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Guest diesel_jim

From playing with the Td5 transducer on the workbench (at work.. :blink: ) i seem to recall the output is "on/off/on/off" as opposed to "hi volt/low volt"

You don't mention what transducer you're using? the V8 EFI one has 2 cables, in & out, and is literally just a switch...on/off/on/off as the shaft spins.

the Td5 one has 3 cables, you need an earth, a 12v feed, and there is the output on the 3rd wire.

Maybe try disconnecting it from the ECU for now (all it will do is give a poor tickover...when you slow to junctions you may find the engine cuts out...although some engines do it, some don't...it's a strange LR thing!)

with it diconnected from the ECU, you can eliminate any back-feeding the ECU might be causing... if it then works, try sticking in a diode in the feed to the speedo (from the "Y" junction into the ECU) to stop aforementioned back-feeding.

But possibly you'll need the proper Td5 transducer to get the speedo working (or at least, working accurately)...then after that you may be able to graft the output from that into the 3.9 ECU.

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Guest diesel_jim
i disconnected the ecu and still no speedo

tested the output from the transducer and it is on/off/on/off

will a 3 wire transducer fit a bw t/case- ybe100530

Like Mo says, yes, they fit straight in where the old cable normally goes.

For the 3 pin plug... use one of the plugs that connect to the later Tdi or Td5 rear brake/slide light unit... it's the same plug (you can buy them from VWP but i'm sure someone has a plug with a few inches of wire you can grab to solder an extension loom onto... i might even have one in the garage, i'll have a gander)

that way it all keeps looking neat and factory-ish.

3 wires.... earth, ignition 12v, and the one to the speedo. jobbie done.

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