Extra brown wire

[John Mitchell <jmitch@snet.net>]

    I put my engine back in today and started hooking up the new wiring 
harness.  In the grouping of wires going to the alternator , there's a 
large multi plug for the alternator, a wire to the Temperature sender, 2 
wires(pink white and yellow white) to the coil,  and a single brown wire 
with a lucar connector.  Any idea what the brown wire goes to?  Thanks 
for any help,   John Mitchell  76 TR6