Installed the Digital 6 Plus in my 84 Trans AM today, the car has no computer and a 4 pin HEI. The car runs very nicely but the tach no longer works. This is mentioned in the documentation and they suggest you might need a Tach adapter. They also suggest connecting the tach trigger wire to the 12V square wave output of the Digital 6. As far as I can see there isn't a separate trigger wire for the tach which leas me to suspect that the tach gets its signal from the coil somehow.

Does anyone know what this adapter is and how it works, or any other way of getting the tach to work?

Thanks.

 

I have a MSD 6AL box and I needed a tach adapter. my tach worked but it was veery funky. hooked up adapter and all has been well...

 

OK so I'm officially retarded. I found the the tach trigger wire buried behind the distributor. Do I hook it up back to where it was before on the -ve coil terminal? The MSD instructions say that only the black and orange wires from their box should connect to the distributor. No mention of what to do with the tach trigger.

 

OK answering my own question in case it helps someone else. I downloaded the advanced docs from MSD and it shows the connection of the tach wire to an adapter (8920) and then to the tach output on the MSD ignition. I connected my tach wire directly to the MSD and it seems to work.