Rotonda

Ernie,

I have a 77, and I am working on the plug that goes into the printed circuit behind the gauges (to add a check engine light in the cockpit for my TPI).




This shows the passenger's side black wire (4th one down) as ground, but it does not address the driver's side black wire (top wire).

I have been tracing circuits until my eyes are crossed, and it seems that this driver's side black wire is also a ground. Is this correct?? If not, what is the function of this black wire?

Thanks in advance for your help!!!

Bikespace

Do you have a multimeter? The '79 wiring diagram I have shows both black wires (and most other black wires) share a common ground. On the gauge side, the "ground" pin appears to go to the fuel gauge, and the questionable one at the top left goes to the negative of all of the gauges and lights, including the fuel gauge again.

If you check the connector for continuity, they should both ring out connected and to the negative battery terminal, at least as far as I can tell from this diagram.

bmotojoe

You are correct, wire #150 is a common dash harness ground. My guess is that the printed circuit board may be divided requiring 2 sources? The main #150 splice area is to the left and down from the printed circuit board on the drawing.