Hi
I have a smiths tachometer which I recently acquired.
It has green, darkish red and two white wires coming out of it
Can anyone advise how to wire it to a MK1 S
Thanks

Its probably safer to quote the part number as there are different types and different ways to wire them up.

I have seen Smiths tachos with those colour wires and the 2 White wires were the RVI pulse external loop wires which either go between the (ignition switch and coil) or between the (coil and dizzy). The Red was 12V and the Green was Earth. But your tacho may be different. If there is a Black wire inside then thats earth and a Red/White wire powers the light globe but yours may not have these inside.

Get the part number and also a pic of the inside circuit board to be sure where the wires are going.

Are you running Neg earth and Electronic ignition? Some RVI tachos dont like electronic ignition and if a tacho is setup for pos earth you will need to swap the connections inside.

Hopefully someone will have the wiring diagram for the exact tacho or one of our resident auto elecs can confirm the wiring.

Here are just 3 that look similar

Need a photo of the back of the actual tacho to confirm where those wires go.
This should also confirm it is an RVI, not RVC as the wiring is very different.
Remove the screw from the rear of the housing and the tacho should pull out from the front.

Also the coding on the front of the dial - RVI or RVC, although intervals may have been changed.

_________________
ex-NSW Police 1970 MK II Cooper S
VMCI #43

Wow GTO I didn’t think it was so complex.

Thanks all for your comments thus far.

My mini has points so no electronic ignition and it is standard negative earth.

I see now that the tachometer is a RVI1003/00

Hopefully the two photos below lead me to the correct wiring

Thanks in advance

Tom

Oops forgot to add the second photo

This is for the RVI 1000/00 with neg earth which looks prety close to yours. Wiring will be as follows

Red is 12V

Green is earth

2 whites are between the coil and dizzy.

If that doesn't work then fit the white wires between the ignition switch and coil. I don't think it matters because the white wire is just sensing the current breaking as the points open and close.

Thanks GTO

Need to source a globe holder now!

Regards

Tom

RVI1003/00 was the type BMC fitted to the last of the Cooper S supplied to NSW Police.

_________________
ex-NSW Police 1970 MK II Cooper S
VMCI #43

I concure with GTO's comments.
The centre terminal (which has the red wire on it) is positive, and this tacho is wired for negative earth.
The white wire (impulse wire) would typically run from the ignition source via the tacho loop to the coil.
If the tacho does not work when wired up, it may be that the impulse wire is the wrong way around. I am not sure about this but the following artical implies this could be the case.
https://www.triumphclub.co.nz/wp-conten ... Smiths.pdf

Yeh I am just not sure if the loop goes before or after the coil. That documant shows 2 styles as well. Might need to try both and see which works the best.

My S is fitted with that same RVI 1003/00 although wired slightly differently.
If yours doesn't work after installing, it can be repaired.
Mine is not very accurate now and I am in the middle of converting it to an RVC type tacho using a circuit board from this place in UK that is intended for Smiths tachos:
https://spiyda.com/smiths-rvi-rvc-conversion-board.html

I'm not too good on modern tech things, but am coping so far.

Just a thought if you need an alternative.

Thanks All for your advice.
Waiting for the weather to warm up before I start the fitting process.
Tom