We've got a homemade engine stand we've used for years to test and tune motors when we build one. Of all the guages we have mounted to it, we've never had a tach so pulled out one today that we knew 'used to work' long ago. We mounted green wire to HEI tach terminal, black to ground, and tried red in a lot of places like battery, resistor, and battery kill switch. What we get is a needle that can bounce sometimes but will never show what rpms we're running, even when we hit the throttle. I know you don't need a resistor to run HEI but sometimes we use a points distributor and like the resistor mounted where it is. Resistor is hooked up currently and motor runs fine. Just need some thoughts on why the tach's not working...Our test motor stand does not have a fuse box. thanks,