QuestionHi Barrie,
I have a 1972 MGB (negative earth). I can't seem to find any information on my electrical configuration.
I understand the thick black (direct from the battery) and where it needs go to.
I have 2 brown wires (excatly same color), each leading (eventually) to the alternator. Thicker brown to the alternator main out, and the thinner brown the the alternator B+ out. These 2 wires should also be connected to the same pole as the thick black.
Here is where my confusion enters... there is a 3rd darker brown wire down there which I can't find anyone talking about.
When I originally removed the wires from the starter (for an engine pull) I could have sworn 2 wires were attached to the same pole as the black and 1 wire was attached to the other pole. Does it matter which pole I attach this 3rd wire to? For expedience sake, I simply have all the wires attatched to the one pole.
Everything seems to work, I just don't know if I can do damage with this set as I do believe the other pole does work differently. By mistake, I had connected the thin brown wire to the top pole, and when I connected my alternator, the start motor started to spin. (not a good thing).
Thanks for any insight you might have for me.
Answer
MGB wiring USA 71-72
Hi Joe.
If you have the early alternator with 5 terminals, then there should be 4 brown wires attached to the main thick terminal on the starter. These are all labelled N (for browN) in the attached wiring diagram.
The thick brown wire goes to the + terminal on the alternator. A thinner brown wire goes to B+ on the alternator. A third brown wire goes directly to terminal (1) on the fusebox, and there is a 4th brown wire that goes to a 4-way connection hidden inside the wiring loom.
The starter has a smaller terminal for the actuator wire, which is white with a brown stripe (labelled WN).
If your car has a different type of alternator, please get back to me with your chassis number so I can look up the appropriate wiring diagram.
