MSD trigger wire to the tach??

[Randy Webb]

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

[Steve@Rennsport]

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.

[Randy Webb]

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)?

[Steve@Rennsport]

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

Trust me, its there,.

[Randy Webb]

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....

[RoninLB]

Originally posted by Randy Webb
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.

[lateapex911]

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!

[TimT]

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