In a message dated 98-05-23 17:55:59 EDT, danray@bluegrass.net writes,
reposting a message from Steve Bettencourt:
> 10) Wiring- Cut a plug from a GM car in the bone yard. The big fat brown
> wire needs a 1/4 inch ring connector. Attach it to the BAT connection on
> back of the alt. The small brown wire goes to the #2 terminal (field) of
> the alt plug. (On mine it is a 14ga red wire.) The small brown wire with
> yellow tracer goes to the #1 terminal (indicator) of the alt plug. (18ga
> black on my plug.)
Dan & Steve, & others,
This is correct, but it only covers one of the possible wiring configuration
one is apt to find on an MGB. There are at least four other configurations
for cars that have a factory alternator, and the earlier models with
generators are all together different.
The other four configurations for cars with alternators are:
1) two wires at the alternator: In this case, connect the large brown wire
and the small brown/yellow wire as described above. Connect another small
wire from terminal 2 to the large BAT connection, along with the large brown
wire.
2) five wires at the alternator: In this case, there will be a large brown, a
small brown, and what appears to be 3 small brown/yellow wires. In reality,
there are only two small brown/yellow wires, as one of them is only a short
piece which goes from the alternator into the wiring harness for a very short
distance and comes right back out again to terminate at the alternator.
Remove this short piece of wire, and wire the remaining 3 wires exactly as
stated above by Steve.
3) two large brown and one small brown/yellow wires: Connect the two large
brown wires to the BAT terminal. Connect the brown/yellow wire to terminal 1.
Connect a short piece of wire to terminal 2, anc connect the other end to the
BAT terminal, along with the two large Brown wires.
4) externally regulated alternators: At the alternator, connect the
brown/green wire to terminal 2, the brown/yellow to terminal 1, and the large
brown wire to the BAT terminal. Discard the black wire (or connect to a good
ground point). At the regulator, connect the brown/green wire to the brown
wire and connect the brown/yellow wire to the brown/black wire. Discard the
black wire (or tie to a good ground point). You can either discard the
regulator or gut it and use the terminals to join the wires as described
above.
Cars equiped with generators (must be converted to negative ground before
making the swap): At the new alternator, connect the brown/green wire to the
BAT terminal, and the brown/yellow wire to terminal 1. Connect a short piece
of wire to terminal 2, and connect the other end to the BAT terminal, along
with the brown/green wire. At the regulator, connect the two brown/yellow
wires together and connect the brown/green wire to the three brown wires.
Discard the black wire (or tie to a good ground point). Discard the
regulator, or gut it and use the terminals for connecting the wires as
described.
A word of caution -- the wiring may not be large enough to handle the extra
capacity of the GM alternator, particularly on the earlier models. Upgrading
the wiring is an easy thing to do, and I recommend it.
For cars originally equipped with alternators: In all cases, the other end of
the large brown wire (or the two large brown wires in 3) which was terminated
on the BAT terminal of the GM unit terminates on the battery connection at the
starter solenoid. Simply remove this wire (or cut off both ends and tie back
out of the way) and run a new wire of at least 10 ga, (8 ga prefered).
Connect one end to the BAT terminal and the other to the battery connection on
the solenoid.
For cars originally equipped with generators: Remove (or cut off both ends
and tie back out of the way) the brown/green wire. Leave the three brown
wires at the regulator connected as described above. Run a new wire of at
least 10 ga (8 ga prefered) from the BAT terminal of the GM alternator to the
battery terminal at the starter solenoid.
I believe this covers all situations, but if there are others I've missed, or
if you have any questions, let me know and I will try to cover them.
Dan Masters,
Alcoa, TN
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
http://www.sky.net/~boballen/mg/Masters/
'74 MGBGT---3000mile/year driver, original condition - slated for a V8 soon
'68 MGBGT---organ donor for the '74
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