Vitesse Tacho wires

[kneescratcher]

I've just tried to melt the Tacho in my MK1 Vitesse. I've just put it in to replace the cable drive tacho thats been superseded sometime in the cars past when the engines been changed to TC 2000
Can anyone enlighten me on which wires go where?

Tacho is Smiths, ex Triumph saloon.
it's got 4 wires
Slate grey I pick goes to the Neg side of the Coil
white - don't know - presumed Swithed side of iginition
Green - don't know - I had it connected to a green wire off the Voltage regulator
note: the Voltage reg is afermarket added when converted to altenator
Black goes to ground

PS we just had our club gymkhana (Hamilton vintage and classic car club - New Zealand) 3rd was collected by a mk4 spitfire and an old Essex was beaten for first by an A30 pickup. I was running first at lunch but can't follow simple directions and went thru some cones the wrong way on the slalom.

[JohnD]

ks,
All Triumph electronic rev counters had three wires, plus one to the illumination bulb, but that was a red wire!
The other three were green, from the volts stabiliser, slate or white/slate to the negative contact on the coil and a black earth.  Try ignoring the white wire if the unit is still round and not puddle shaped.
John

[kneescratcher]

I did have the green connected to the switched side of the ignition and ignored the white with no luck so I'll give it a go connecting to the stabiliser
what output from the stabiliser do I look for?  all the ID's have worn off

[Nick Moore]

What sort of gymkhana was it? The Triumph Owners Club in Christchurch (also NZ) usually have their gymkhanas on grass. Easier on the cars, and too much power results in quick exits with the world going round. It's always good to see a Herald beat a Merc, something that would never happen on bitumen!

[Nick Jones]

There are two types of 6 cyl triumph tacho you could have.

Older ones are RVI current sensing. They will have RVI plus a number somewhere on the dial.  They will also have three connections plus earth and light.  One male bullet (connect to distributor), one female bullet (connect to coil -ve).  This means that the short wire between the distributor and coil is replaced by a long wire that passes through the tachometer. The spade connection is the supply and needs to connect to an ignition switched 12v.  Don't connect is to the output side of the instrument voltage regulator or it will only work intermittently.

Newer ones are RVI voltage sensing.  They have RVI marked on the dial. They have two connections in addition to earth and the light.  The bullet connection goes to the coil negative.  existing wire between distributor and coil remains in place.  The spade is the supply as before.

Note that the older ones rarely work with electronic ignition.  The newer ones work with most.

Good luck!

Nick

Newr one

[kneescratcher]

Nick M
We had a fantastic Gymkhana here in Hamilton.
Most activities were slower the better and didn't rip up the farmers paddock too much
the slalom was the only activity were quicker was best. the best times around this were done by those that kept a steady pace. Those like me that spun the wheels lost time trying to correct it and consequently taking the long way round. or worse - like me that forgot to look at the instructions.
a very enjoyable day had by 30 cars of varying vintage from Model A's to Honda N360's

Heralds beating merc's may encourage some debate

[kneescratcher]

Nick J
That makes sense. this tacho has RVI 2631/00 and 4 wires so by your description should be the early current sensing type. the marks are exposed when you take the thing apart otherwise hidden by the inside bezel
When you examine the white Wire path it is just a continuous loop through the Tacho coil a couple of times so makes sense that this will replace the Coil to Dizzy wire.
Thanks for your Help

I guess a sparky could explain how the coil reads the current. I remember some where in the dark past been told this at polytech

Cheers