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MG Midget and Sprite Technical - Wiring question

Anyone help me with this? I'm rebuilding a 67 sprite and am making my own wiring loom out of 2 and converting to alternator etc. That's all fine, but can anyone advise about the white wiring to the tachometer? There is just one white that had been cut off short and the wiring diagrams and books show some sort of white loop to the post at the back of the tacho. Can someone advise where the whites should come and go from/to or a picture would be nice. Thanks in anticipation
Chris
C A Ennis

The white loop in and out of the tacho is a feed from the ignition to the live side of the ignition coil.
Dave O'Neill 2

That always worried me slightly Dave. Is there any advantage to installing a fuse in the tacho wire?

It looks to me like a big short in the coil/wiring could use the tacho as a pretty expensive fuse if the supply fuse was too big to protect it.
Greybeard

""" It looks to me like a big short in the coil/wiring could use the tacho as a pretty expensive fuse if the supply fuse was too big to protect it.

Well DUH...Yeah.... what else would want a tacho for ?

haha

prop
Prop and the Blackhole Midget

Which tacho is it?

As I understand it there are two types of tacho, one has the wires in and out at separate terminals.

Mine is like this and was built in 1966.

Connection is by female socket carrying ignition power in via an insulated connector and the live feed exits the unit off a female terminal, thus if it becomes disconnected the dangling wire is at earth potential

That is why I have never sought to change the fitment method

The other type simply has a loop of white wire connected by a plastic clip to the back of the tacho.
Bill sdgpM

The two types are RVI (inductive) and RVC (capacitive) and refers to the method needed to drive the tacho. The RVI type senses the current pulses caused by the points opening and closing and requires the use of a loop in the white wire feeding the coil. The RVC type works by sensing the rapid voltage rise as the points open and is connected to the white with black tracer wire that connects to the points.

Rob.
Rob aka MG Moneypit

Thanks all much appreciated. I've sussed there's a bit missing which i'll now get to complete the picture
C A Ennis

This thread was discussed on 24/01/2016

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