tachometer wiring question

[body by fisher]

1-does a tach need a ground?
2-does it require a filter?
I have a tach from a 1977 trans am 6k and i have yet to get it working, there are 3 or 4 posts for wires

 

[camaro lover]

yes they need a ground. I don't use a filter. my new tach has 5 wires. 1 for ground, 1 for constant positive, I for key on positive, 1 for positive when lights are on to use tach light when dash lights are on, and green to tach wire on side of hei distributor. I would imagine most are the same.

 

[77RS]

1-does a tach need a ground?
2-does it require a filter?
I have a tach from a 1977 trans am 6k and i have yet to get it working, there are 3 or 4 posts for wires

Yes, the tach will need to be grounded. The grounding for the tach is received through the rear printed circuit. On Trans Am, the clock and tach are grounded at the same location. Looking at the rear of the tach, the upper left blade is for tach signal, the upper right blade is for 12V+ (switched). The tach will not receive constant power. Hope this helps! Daniel