MSD trigger wire to the tach??
 

I swapped out the old engine in my '73 for a 3.2L and am trying to figure out how to wire up a MSD 6AL. Of course, the coil was changed out too, so I am trying to figure out how the tach is going to get a signal. I haven't found this in the many MSD threads, I guess because most people are just swapping a MSD for the stock Bosch box.

The MSD green/violet with the connector goes to the mag pickup in the distributor -- is this the trigger wire for the tach??

If not, where is the trigger wire ??

Or do I plug some different wire into the slot on the MSD unit marked "tach output terminal"?? I thought that was for an auxillary thing (like a shift light) or for the dreaded tach adapter.

The wiring diagram appears to show a red/brown wire (#43) that runs from the bottom of the tach (and switches schematic pages) thru some connectors to the rear elec. panel, exiting at pin 9 - it might change color to black/purple but the diagram is so small I can't tell. Does this have anything to do with it?

the white MSD wire is not used, since I am using the green/violet wires

I've already connected all the other wises as follows:

the fat MSD red goes to the hot starter lug

the fat MSD black goes to a chassis ground

orange & black go to the coil terminals

the thin MSD red wire goes to a switch +12 V source

Randy:

Plug the car's black/purple tach trigger wire into the tach terminal at the end of the MSD case.

That usually does the trick on those early cars.

Thanks --

....

how do I find the car's black/purple wire? i.e. what does it connect to (or what was it supposed to have connected to, before I pulled everything apart)?

You'll find the black/purple wire in the area where the Bosch CD box used to be.

Trust me, its there,.:) :)

Thanks - I'll look for it. I'm assuming it's a loose wire not inside the black sheath of stuff that plugged into the CDI box....

mine was deep inside the harness running on the driver side. There was a 2 into 1 connector in there.

Mine is hanging our looking for a distibutor point set up to attach to. I too am in this same boat! Except MY situation is an MSD6al with Crane optical setup in the dizzy...and NO tach!


Thanks Steve! I'm gonna go try that!

Chances are your going to have to get a tach adapter so that your tach works correctly with the MSD.