Tachometer reading double

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Tachometer reading double

Post by Adam » Fri Nov 25, 2016 5:54 pm

New to the forum.

I have a Mk II tiger with a 'Smiths Motor Accessories' tachometer that reads precisely double the correct reading at all times (I have checked against a hand held meter). It is wired correctly to one end of the ballast resistor, as per the wiring diagram. The body of the tach is earthed to the chassis.

It even says '8 cyl' on the face of the gauge but reads as if it were a 4 cylinder gauge.

Is there any way to adjust the reading? or is this a problem that others have encountered? I would like to sort it out and I am hoping that the wisdom here can help.

Thanks for your thoughts.

Adam Moody
Last edited by Adam on Sat Nov 26, 2016 12:13 pm, edited 1 time in total.

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Post by Pierre » Fri Nov 25, 2016 10:22 pm

Too much wheel spin :D

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Post by gvickery » Mon Nov 28, 2016 10:47 am

Adam. This possible answer was passed to me by David Herning of Herning Motorsport:

"It can be adjusted via the potentiometer inside the case on the circuit board, but it would be better to send the unit to Speedy Cables to have the circuit board replaced with a system that picks up the signal from the negative side of the ignition coil,rather than a pulse via the white wire,this is more reliable.
Would be of interest to know what the number on the bottom of the dial is,could still be an Alpine tacho re worked and have "8 cyl" put on to it"

This eBay listing shows the model number for the MKII tach
http://www.ebay.com/itm/1967-Sunbeam-Ti ... 2504205486

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Post by Adam » Tue Nov 29, 2016 11:49 am

Hi Graham & David

Thank you for the information. Very useful.

The numbers on the face of the tacho are RVI 2812/03

I would post a picture, but I haven`t yet spotted how to do that on here.

Adam Moody

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Post by dpuzey » Tue Nov 29, 2016 4:13 pm

You could try Spiyda Design,

https://www.spiyda.com/magento/index.ph ... onics.html

They make a board you can fit to your rev counter and adjust. Very helpful.
Dave Puzey
1965 Midnight Blue Tiger
1958 Speedwell Blue Sprite
1967 Mid Grey SWB Land Rover
2011 Scuba Ford KA

Used to own 1985 Targa Red Rover 3500 TP Vitesse

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Post by Adam » Wed Nov 30, 2016 12:18 pm

Interesting. Thanks.

Adam Moody

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