do you have a small transformer or something putting out 5-v approx , or 3 - 1.5 v batterys or a 9 v battery & just touch it to the guage for a second the guage should swing across , hook + to the low side & - to the high side, , the tach has to be hooked to a running engine , you need a ground to the case , signal wire hooked up form the coil & + wire hooked up as well