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Speedo graph tachometer wiring

Posted: Fri May 07, 2021 1:24 pm
by Dearg1275
Can anyone tell me how to wire this Tachometer? It’s going in a negative earth car as a stop gap until I get it’s Smiths unit back from speedy cables. My guess is that it earths through the body, the red is to live and the green goes to contacts side of the coil. Is there any way to check the polarity of the unit before I have a 50/50 chance of frying it?
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It would not be a great loss if it went up in smoke but a working tacho is quite useful.

D