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Re: Help Volvo MD5A idiot light wiring
The thick red wire is the power delivery to the battery.... it is a positive lead.
I am puzzled as to why the white lead goes nowhere, but the black and white leads look very much like the field excitation leads for the alternator rotor.
There will be a regulator somewhere too, perhaps on the other end of that black lead.
Tell me, when the motor is started and revved up to (say) 2000 rpm, what is the voltage across the battery leads? It should be about 14 V, perhaps a bit higher.