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Discussion Starter · #1 ·
I have a Autometer 5 inch monster tach and my original tach is also working.
Yesterday the car didn't start and some blue fumes come out of the hood. It behaves as if there is no ignition. I disconnect the tach wire and it starts.
Both tachs are connected with same wire to the distributor.
Also last winter the car burned a MSD 6 igniton box. So there is a problem with the igniton I disconnet all MSD stuff and and the standart distributor and coil is put back.

One of my friends told me he has same problems when he uses 2 tachs like mine?
Could it be the tachs?
 

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Curious about your post, I did some research, as I'm going to need to know how to rewire my '69 next year anyway.

You and your friend have a very basic problem--wiring instructions.

Autometer instructions very clearly state NOT to connect green wire from tach to coil with MSD. My concern here is that you have one factory tach that operates off of the negative side of the OE coil, which is the distributor lead (w/o MSD, and points triggered, I assume), and you suggest that you have "both tachs connected to the same wire at the distributor". With the MSD6, the instructions indicate connecting the Autometer tach to the tach terminal of the MSD unit, NOT the coil (which is the distributor w/o MSD).

I suspect that in the confusion of the connections you have wired incorrectly, which might allow for both units to temporarily function, but ultimately fail, as in yours and your friend's case.

I'm sure that, if you have not already, MSD and/or Autometer would be happy to provide some technical assistance to unsderstand how the Autometer tach gets wired properly, and the proper connection to the dash oem tach.

I believe it was wrong to connect the two together on the MSD. As far as your 'blue smoke' problem that was corrected by disconnecting the tach and reinstalling the original ignition, and disconnecting the tach to get the engine to start, I suspect that the two tachs together are drawing too much current, preventing proper ignition voltage. If the coil does not saturate properly, there won't be enough voltage to fire the plugs. As both tachs appear to operate on a 'voltage spike' signal, it stands to reason that not only are they drawing current from the ignition, but both tachs are probably reading incorrectly as well.

I'm sure MSD or Autometer would have a solution for you. IMHO, connecting the Autometer to the MSD tach output, and the oe tach to the negative side of the coil 'should work' trouble-free', but tech support would have the final say.

If I'm wrong in my analysis, somebody correct me. I need to understand this stuff myself. I plan on using MSD6AL and an Autometer tach myself (though not w/ the oe dash tach).

My only other question would be...why would you want to have a functioning dash tach in tandem with that nice Autometer anyway???? Just my .02.

Good luck.

JR
 
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