MSD Fast Tach wiring.....only 3 wires ?

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mbaird

mbaird

mbaird
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A friend gave me an old MSD Fast tach and it only has 3 wires.... Red / black / white

(I am not running MSD ignition)

Red - hot
Black - ground
White - ?...usually lighting I thought....

NO green !

I have scoured the net and can't find any reference to wiring this to my Chrysler electronic ignition.
 
I would ASSUME red power, white light and black negative side of coil.
 
mbaird said:
A friend gave me an old MSD Fast tach and it only has 3 wires.... Red / black / white

(I am not running MSD ignition)

Red - hot
Black - ground
White - ?...usually lighting I thought....

NO green !

I have scoured the net and can't find any reference to wiring this to my Chrysler electronic ignition.
Click to expand...

What does MSD say?
 
I have not called them yet.
And I am not finding any 3 wire diagrams online.
 
Maybe remove the back of the tach and see if there's a fourth green wire? Or blue in some instances.
 
tried white on lighting wire , red to hot , grounded black momentarily and got no lighting but needle jumped backwards a little...

Hmmm....Rusty might be right about black to coil...I will open it up tomorrow and check for green then call MSD if not.
 
mbaird said:
tried white on lighting wire , red to hot , grounded black momentarily and got no lighting but needle jumped backwards a little...

Hmmm....Rusty might be right about black to coil...I will open it up tomorrow and check for green then call MSD if not.
Click to expand...

he usually is !
 
I called MSD tech line and they said there should be a green wire as well.....but the
Tech had to ask some of the others before answering.....

Yet there is no green wire...
 

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I have an older tach with 3 wires. Red is hot, black is ground, and green is coil. The light works all the time when car is turned on. Check it with a multi meter. See if the black is ground. If so, it's easy to figure out the other 2.
 
I have an older one that has Red +12v Black Gnd and Grey coil (-).
It does not have dimmer option. If Ignition is on, light is on.
 
mbaird said:
I called MSD tech line and they said there should be a green wire as well.....but the
Tech had to ask some of the others before answering.....

Yet there is no green wire...
Click to expand...

So MSD made and sold it and they don't know? I sure don't LOL
 
Ok.....so if I hook red to + and black to (-) the tach jumps from 1000 where it seems to rest when disconnected to about 1300.....

But when I touch the red to(-) and black to + on the battery the tach zeros out.....

I am assuming that the white is the signal wire.....

Which way is correct? It seems like the tach should zero out once the ignition is switched on before starting engine.

Signed,

Dazed and Confused
 
Some meters (my little Autometer) "stops" the needle wherever it "is." EG let's say it's working, engine running, and you rev the engine to 2K and shut off the key. The needle on the tach stops there at 2K.

I bet you are on the right track, tho. black ground, red ignition power, and white the trigger.


What are you using for ignition system? MSD / other CDI may not trigger it.
 
How attached to that old one are you? $100 for a new tach with shift light maybe?
 
I got it going....
Red (+)
Black (-)
White ( - coil)

I was just over thinking it and didn't want to fry the tach....

I'm running good ole Mopar electronic...

Didn't want to spend the $100 and kinda like the old school look of this tach.
I already have close to 15k into the car and $100 is a new Tire for my KTM or a new hockey stick or a day skiing at Alta or a 1/2 dozen ACC arrows or....

I might have too many hobbies !....lol
 
Hmmmm..... 3 wires....24 hours...

This car should be ready by 2022....
 
mbaird said:
Hmmmm..... 3 wires....24 hours...

This car should be ready by 2022....
Click to expand...


Funny! We have all had projects like that I think. I have spent the last 3 weeks trying to solve a leak with my water outlet (tried two new types of gaskets, and finally a new water outlet). Thought for sure "I fixed it" only to see later that although it was better it was still dribbling all over my nice clean and freshly painted intake manifold. What I finally realized is one bolt was not getting tight enough (and I didn't want to strip the threads out) so all I had to do was borrow a thread cleaner from Auto Zone, clean out the threads on the intake manifold, and get 1/4" longer bolts. That seemed to do the trick....but man, I swear I could have pulled the engine and put it back in the amount of time I spent on that stupid water leak..
 
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