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Fri May 19, 2017 10:08 pm

1970 Ghia:

Here's the scoop and I'll try not to be to wordy. I recently wired my ghia w/a new wiring harness and having mental/tech difficulties wiring the speedo.

Look at the wiring diagram, the ground from the fuel gauge, goes to the speedo then to the clock.

Looking at the original wiring diagram, there's a black wire that appears to connect from the fuse box to one of the lights (K3).

1.Is there two wires coming off K3? the black wire that goes to the fuse box and the blue/green wire connect to K3?

2.Does the ground wire that comes off the fuel gauge to the speedo connect to the clip I circled in yellow with an yellow arrow pointing to it??

3. how does the upper lights get grounded, letters "A-F" what are those connectors I circled in blue with the blue arrow?

Thanks!

Fri May 19, 2017 11:25 pm

K2,K3 & K5 get a ground from the sensors that drive them. The photo where you have labeled "Ground?" is the tab where the black wire from the fuse will provide the backing 12volts. That tab is insulated from the speedo body but common to each of the three bulbs.
Nicholas

Sat May 20, 2017 7:37 am

Mrfun2fly wrote: 3. how does the upper lights get grounded, letters "A-F" what are those connectors I circled in blue with the blue arrow?

Those twin tabs circled in blue are to connect ground wires for all the upper bulbs (what you call A-F). They get power only when switched on.

For the lower three bulbs, the best way to think about them is that their circuits run opposite to everything else. They always have power, provided by the tab at the end. That's why they are electrically isolated from the rest of the gauge. In the case of the oil and battery lights, they turn off when the engine is running because their sensors deprive them of a ground, disconnecting the circuit.

Sat May 20, 2017 10:26 am

jason_hamilton wrote: Mrfun2fly wrote: 3. how does the upper lights get grounded, letters "A-F" what are those connectors I circled in blue with the blue arrow?

Those twin tabs circled in blue are to connect ground wires for all the upper bulbs (what you call A-F). They get power only when switched on.

For the lower three bulbs, the best way to think about them is that their circuits run opposite to everything else. They always have power, provided by the tab at the end. That's why they are electrically isolated from the rest of the gauge. In the case of the oil and battery lights, they turn off when the engine is running because their sensors deprive them of a ground, disconnecting the circuit.

Two years after wiring my speedo without understanding what the heck's going on, an explanation that makes sense.Thanks Jason.