Tach issues with MSD 6 Hemi

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Map63Vette

Map63Vette

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So is anyone out there running an aftermarket tach with an MSD 6 Hemi box? I have a little Actron Acrotach I got at a swap meet and like the small form factor, but when I hooked it up to the 12v yellow tach line from the MSD box I'm getting nothing out of it. I know MSD sells a bunch of different tach adapters for different setups, but I was wondering what other people had done. The tach adapters are almost as expensive as a new tach anyway, so if I just need a different tach I may consider that.
 
I have an Autometer tach and shift light. They both work perfectly with the Hemi 6.
 
Map63Vette said:
So is anyone out there running an aftermarket tach with an MSD 6 Hemi box? I have a little Actron Acrotach I got at a swap meet and like the small form factor, but when I hooked it up to the 12v yellow tach line from the MSD box I'm getting nothing out of it. I know MSD sells a bunch of different tach adapters for different setups, but I was wondering what other people had done. The tach adapters are almost as expensive as a new tach anyway, so if I just need a different tach I may consider that.
Click to expand...
I believe the yellow wire is a 12 volt source. you would need a tach hook up for any tach you use.
 
I have a 70s pedestal SW tach custom calibrated which required no adapter - but.......

........ my Factory 'in dash' tach DOES.

I used the MSD 8920 for my factory tach.

FWIW...I contacted MSD and asked them if Id need an adapter with my SW ...and they said I would....shows how much they know!

Using the adapter all comes down to whether your tach is current or voltage signal driven.......

StewartWarnerTach.jpg
 
Yeah, I finally got it working, but had to be rather clever. After I installed my Megasquirt setup I tried to run it straight off of the tach output line the MS has, but with no luck. I ended up buying a tach adapter, but wiring that alone still didn't work. I ended up configuring the MS to act like it was firing a coil (basically opening and closing a ground), and wired in a pull-up resistor to get 12V at the tach adapter. With a little tweaking of the resistor size I got it to work, but with my latest job on the car I pinched the tach trigger line in the steering column mount and fried the wire. Thought the car was going to go up for a second with all the smoke from such a tiny wire.

I've since pulled the whole setup and am looking into new tachs again. I still like the small <3" ones, but there aren't too many and a lot of the really small ones aren't electronic, so they don't work directly off tach output lines of computers, but I really don't feel like putting the tach adapter back in as that setup was cobbled together at best.
 
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