Looking at the Bentley manual, there are only three wires from the alternator for the 1982 diesel.
Two fat reds - both go to the battery + terminal.
One thin blue wire - goes to the charge light on the dashboard via three consecutive single pin connectors.
I believe the alternator charge light circuit is often used as the exciter line. So that would be the blue
The alternator is grounded via it's mountings.
If you have a negative wire, it should be brown or a bare braid.
If as you suggest, the alternator is flattening the battery, then I suspect that it is a fault with the alternator or at least the rectifier unit or voltage regulator mounted on the alternator.
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The "ignition" reference is a bit confusing...
The charge light has a +12 volt ignition live feed.
And the return path for the light is the blue wire from the alternator.
When the alternator is at rest, the blue wire is at or close to 0 volts and the light illuminates.
When the alternator is running, the blue wire carries battery voltage and therefore "cancels out" the charge light circuit, thus putting off the charge light.
See if this helps.
BL = blue wire to instrument cluster.
R = Two red wires to the battery + terminal.
The thin lines for the grounding refer to being connected directly and not using wires.
Ignore the line saying starter - it is not a wire. Just a poor location for the label.
1983 Tin Top with a poorly DF and 4 speed DT box.
1987 Electrics and a DJ engine.
Maybe one day I might get it finished
mg]
