Alternator wiring

[Kneale Brownson]

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So I've performed the Bentley test regarding battery/ABS/Brake warning
lights on the dash not going out when the engine revolutions increase, that
is, disconnect the little blue wire (turns out my little blue wire is
sheathed in a heavier black insulation) and turn on the ignition, and the
lights don't show.

The Bentley says that means there's a problem in the little blue wire.  It
goes to a connector mounted behind the passenger side headlight.  The wire
from the alternator to the connector has good continuity.  That connector
is corroded terribly on both sides, so I've CRC'd, filed (small flat file),
sprayed with an electronics tuner cleaner/contact enhancer from Radio Shack
and blown it off with air.  Still have the warning lights when engine revs
increase.

The little blue wire enters a harness just in front of its mounting clip
that disappears toward the core support.  I presume it goes to the dash
somewhere.  Is it exposed somewhere I can test continuity?  Do I have to
take out the instrument cluster to fix this crap?  Can I run a temporary
wire somewhere until we get to warmer weather?  Working on this problem in
a snowbank with 20-degree F temps is not fun.

What gets me is everything was working fine until I ran through a bunch of
slush Saturday.  That's when the warning lights and sub-12-volt reading on
the gauge appeared.  How did that circumstance cause the little blue wire
problem?
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