I have a new 71 ss gauge cluster with all gauges, and all new harnesses by m&d harnesses. Dash, engine and forward lamp harness's. The problem I am having is on the dash harness there is a wire coming from the harness that states tach and that goes thru the firewall and hooks directly to the hei, I have everything else working but when I look at the back of the dash circuitry I don't have any wires going to either one the 3 post on the back side of the tach and there is no place where the circuit board gets attached to it either. also to the left side of the tach on the printed board there are two other post that predrude thru the circuit board and are threaded can anyone tell me if there are supposed to be nuts on them. Man I sure could use someones help here. :D
Joe

I have a new 71 ss gauge cluster with all gauges, and all new harnesses by m&d harnesses. Dash, engine and forward lamp harness's. The problem I am having is on the dash harness there is a wire coming from the harness that states tach and that goes thru the firewall and hooks directly to the hei, I have everything else working but when I look at the back of the dash circuitry I don't have any wires going to either one the 3 post on the back side of the tach and there is no place where the circuit board gets attached to it either. also to the left side of the tach on the printed board there are two other post that pretrude thru the circuit board and are threaded can anyone tell me if there are supposed to be nuts on them. Man I sure could use someones help here. :D
Joe

The tach wire pulls out of the main harness plug. The circuit board should hook to the back of the tach with the little nuts. Everything except the clock hooks up that way. Maybe you have a idiot light printed circuit ?

"to the left side of the tach on the printed board there are two other post that pretrude thru the circuit board and are threaded can anyone tell me if there are supposed to be nuts on them"

Yes the two posts are the tach power and pulse inputs.



http://www.chevelles.com/showroom/data/500/70-72_tach.jpg

I have rechecked several sites on the computer and they all show the circuit board for the ss tach gauge as open where the circuit board does not connect to it the tach, I really don't think there all wrong. anyone else know?
Thanks
Joe

Hey Joe, Where are you located in Jersey? My buddy just did this conversion for me with all the harnesses and new gauges. I will call and ask him.

Hey Joe, Just called my buddy. The circuit board runs the tach. There are no wires that hook to the tach. The wire you are speaking of does go to the Distributer. Thats it.
Double check the Printed circuit board.

The tach gets power and the pulse input from the two threaded posts shown it the pic. If you follow the copper traces on the circuit card you will find that they come from the PC connector. You can follow them in the pic. The one identified as +12 also supplies power to the oil light, fuel gauge, temp gauge etc. The trace for the pulse signal or coil connection feeds the tach only. Put nuts and flat washers on the terminals connect the brown wire to the coil or dist TACH connection.

http://www.chevelles.com/showroom/data/500/70-72_tach.jpg

Thanks to all for the input, there were a few that thought I might have the wrong circuit board, I failed to mention that this is a complete kit along with the circuit board and M&D wiring harness for that dash with all gauges.
Thanks
Joe