Went direct to battery power and no change. When I say it runs backwards it moves to zero when I accelerate. I wired in another tach I had lying around the shop and it works. so I think the old Electro-tach with new solid state internals does not like my ignition set up. I've read I could try a tach adjuster but that does not make sense to me. I think I will return this tach an look for another one that will work.