I changed out my factory rally instrument pod for one with a tachometer.

does anyone know how to run connections for the power? I got the tach connection part on the hei, just not where to hook up 12 volt power and ground on the tach itself.

The cluster's main electrical harness distributes power to the gages and lights via a plastic circuit board similar to what I have shown below. It's usually on the very back of the cluster. 

Once you install the tach in the cluster and its connections mesh with those in the black receiver, then the circuit board should go on the back of it and distribute the power and power up the tach for lights, 12V, and ground. Obviously the tach signal was to come from somewhere else, which you said you've established.

 

If you wiring is cut up behind the dash, let us know.

Just need to know where the signal from hei connects.

Here is the wiring diagram for a 70-71 GTO. While this is not the same as your 73, the wiring should be similar.

The HEI was not available until 74 right?

Correct - the tach output from the HEI should match the stock, non-HEI wiring. Your 73 Grand Am is based on the Colonade style of A-body cars. Pontiac used, essentially the same dash and gauges in the Lemans/GTO/Grand Am body from 73-77. I am not aware of any gauge/wiring modifications they did just for the introduction of HEI.

I guess I needed to know where the connection from the tach landed. The print you sent was not showing a tach.

You're right. Sorry about that.

 

Here is the uber simplistic wiring diagram. I would remove the tach from the cluster and look at the back of the actual gauge. It should have some sort of markings for each electrode. Essentially the "green" wire is the signal/pulse line from the coil to the tach gauge. Black is ground. White a 12V light source or bulb, and red is the switched 12V source for the gauge.

Edited June 12, 20187 yr by Frosty

HEI should have a "tach"  signal stamped on it. 

 

 

I guess I am not making myself clear, I need to know where the lead from the HEI tach plug lands on the tach in the instrument cluster.