Aftermarket tach installation question

[bljones]

I am installing an aftermarket tach in my 86 syncro. Installed red wire to ignition switch, black wire to ground, green wire to neg terminal of coil, same way i installed the tach in my 181.

Uh-oh. Getting an erratic reading- the needle is bouncing between 2000-3000 rpm at idle. Hmm, maybe i am getting some interference through the ground, methinks, so i connect the ground wire directly to the battery ground- same result. Idle is lumping along at 800rpm as usual, but tach is jumping from 2000-3000 rpm.

So, I am thinking that the tach input- (green wire) should be attached somewhere other than the coil, but where- anybody have any answers?
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OG JHC
Author of Original Rant #1
"It stingd itself to dead... now that is control on you"

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[Randy in Maine]

Do you have an electronic ignition?

Been here?

http://www.egauges.com/pdf/vdo/0-515-012-037.pdf

[bljones]

That was my first stop, randy, based on advice you had posted on this same topic earlier. No joy.

Where does the factory tach get it's input from? I am a complete moron when it comes to wiring diagrams, and what i have been able to discern from the bentley wiring diagram has not helped me at all.
_________________
OG JHC
Author of Original Rant #1
"It stingd itself to dead... now that is control on you"

2%

[msinabottle]

A wire off the coil! Look up my post on Winston's tach, I tapped into one of the connectors on the coil, ran that up to his cocput through one of the core RAMMING SPEEEEEEEED beams and then up through the heater hose grommet to the tach

I got a new cluster ouf of an '85 and got the stock tach with the quite useful shading to tell you when you are being good to your Vanagon. With that I also got the digital clock, which keeps perfect time, unlike the one it replaced.

Best!

[Randy in Maine]

Mine came off the "1" or "-" side of the coil and runs right to the tach.

[mightyart]

I used the coil also.

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