12 volt tach on a 6 volt positive ground system

I know. Maybe I didn't explain it very well in my previous posts 16 and 17 but it is a standard 12 volt batt neg ground. I'm not very electrical savvy but the guy I worked with at an electrical shop said the batt does not know if it is pos ground or neg ground so I tried positive grounding a 12 volt batt on my tach at it has been working fine since 2015.
 
If I am following you correctly, tach red to (+) battery post and tach black to the (-) battery post is normal 12v wiring hook up. Not sure where this would be considered pos grounding. Connecting the pos battery post to ground doesn't do much of anything as far as I can see. Maybe I'm missing something, but looks like you just have the tach connected a seperate 12v source.
 
JSeery said:
If I am following you correctly, tach red to (+) battery post and tach black to the (-) battery post is normal 12v wiring hook up. Not sure where this would be considered pos grounding. Connecting the pos battery post to ground doesn't do much of anything as far as I can see. Maybe I'm missing something, but looks like you just have the tach connected a seperate 12v source.
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I think that is what he's done. However, the signal from the coil/distributor has the wrong polarity, which was the biggest problem I've faced. Maybe the tach he has doesn't care about the polarity of the signal, but all of them I've dealt with do.
 
And the signal from the coil is half the voltage what a 12v tach expects to see so sometimes they don´t even read the signal.
As i said earlier that tach must be a real tolerant one don´t expect your average tach to do that.
 
Sorry to clutter up the board, but I need to get a picture to "erl". I can't send one via a PM and the board doesn't have an email for him, so I'll post it here.

Again sorry for this misuse of the board.
 

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