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MG MGA - dash wiring question 2

I guess my engineering knowledge of dc circuits is lacking, and I'd really like to understand what I'm doing with this dash wiring. First question; there are two brn/blk wires from the dash harness, one going to the horn, and the other to a bullet connector and then to the main harness. Does it matter which one goes to the horn and which one goes to the bullet connector? Second question; the tach seems to get two black ground wires (that are connected) attached to its bracket, while the speedo gets only one. Why is this, could the speedo get the two grounds instead?
This is probably pretty basic stuff to a lot of you, guess I'm catching up!

Thanks, George
George G.

The nuts on the tach and speedo are just convenient places to tie the grounds together. The retainers may also provide ground to the metal dash through the painted surface. If memory serves me I do believe that the ground also grounds to the firewall bulkhead somewhere around the Flasher unit.
... CR
C.R. Tyrell

Horn circuit here:

If I recall correctly, you have to open the back of the horn switch to connect the wires to screw terminals inside. The switch doesn't care which screw is which, not polarity sensitive. If you have two wires Brown/Black, then connect those together with a snap connector.

All black wires are created equal and all are ultimately connected together and to ground. They are interchangeable, so connect them to whatever grounding point is closest to their emergence from the harness. When you see two black wires in a common ring lug connector, that is the way they are daisy chained together for common connections.
Barney Gaylord

This thread was discussed between 31/08/2016 and 01/09/2016

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