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MG Midget and Sprite Technical - Tacho question

Hi All,
Had a great weekend bimbling around the twisty bits in the sussex countryside, but out yesterday, noticed my tacho had stopped although it was working when I left home. I'm guessing its a wiring / connection break as there are some quite impressive potholes in sussex roads- but my question is: Is there any way of testing a tacho to see if it is working ( apart from obviously driving it) to see if I have a wiring fault or a tacho unit fault?
Cheers colin
colin frowen

The tacho runs off the same fuse as the fuel gauge & wipers, so if they are working you should be getting power to it.
There were different tachos - what year is the car?
Paul Walbran

Some of them need a tap to get going (stick spindle...) when the engine's running.

A

Anthony Cutler

Hi
Its a 1972 mk III midget - the fuel gauge was def working but ( unusually) didnt need the wipers yesterday.
The tacho was def running whenI set off- could it still be a sticky spindle?
I will check out all the wiring ( & the wipers etc tonight)
Just wondered if there was / is a test at all?
cheers colin
colin frowen

According to the offical manual, the tacho should be current loop type. It's easily identified by two white signal wires to bullets in the back rather than a single white/black one.

If it's the current loop type and the engine is still running, that should rule out a problem in the signal circuit, as it's in series with the coil primary - if it fails the coil stops as well.

The later voltage sensing tacho with the single white/black wire is in parallel with the coil primary, so a fault could develop in the signal circuit and the engine still run.
Paul Walbran

Hi Paul
Thanks very much- my feeling is its a wire off as the car was running really well but will look tonight- so thats me upside down in the footwell( again!)
cheers
Colin
colin frowen

Colin - the test for this is very simple - as Anthony said - start the car, and tap the glass on the rev counter - if it moves, it's sticky - if it doesn't then there's possibly a loose wire, or something more exciting, but, seriously - tap first, worry second!

Yup - it could do it mid-trip - or at any other random time it decides - it's a midget!!!!
rachmacb

Hi
Thanks all- will give it a bash tonite.
Cheers :-)
Colin
colin frowen

Colin,
as rach's put >> tap first << perhaps bash later :)
Nigel Atkins

Hi all,
Gave it a gentle tap (!!) & it burst back into life!
Thanks to all for the great advice-& I thought it was only mini's that had horrors like this :-))
Cheers all & thanks
Colin
colin frowen

I have to tap mine at almost every start up but there was a time when I didn't need to and I thought I must have done or added something to bring about a cure but then later it went back to needing a tap at most start ups again - I've no idea why it stopped stopping and started stopping again
Nigel Atkins

This thread was discussed between 14/05/2012 and 15/05/2012

MG Midget and Sprite Technical index

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