Tach problems...still
 

So I spent last weekend tracking down and installing a new (used, but working) tach. Mine had been dead for a year, but finally got around to replacing it...

So if it wasn't the tach... what could it be? Where does the tach get its signal from? Can I test for a signal?

Have you changed the S.I. batteries on the board? Thatcan cause a weird tach...

Unfortunately I have... which brought me to the tach itself. Checked the fuses too...