Ken Anderson,
Spreading the one problem terminal did the job and my headlight warning light works now. Took it apart twice and checked. All's good now.
Geek's 65,
Using your information, and after ensuring a good firewall connection (see above), I was able to get voltage at the
ACC LPS buss. Thanks much.
Two remaining questions.........
for now anyway.
1. My earlier question remains unsolved -- "Not only are the
ACC LPS terminals
not showing on the wiring schematic provided by Lectric Limited, they're not in the A.I.M. nor the Service Manual either. The POWER WINDOWS terminals are showing.....the other two are not."
2. Why would Chevy configure the two terminals
ACC LPS on the fuse panel in the way that they did?
- when dash lights are off there's no (or negligible) voltage at those terminals
- however, voltage progressively increases with the brightness of the dash lights -- 2 volts (at minimal brightness), then...3...4...5...6...7...8...9...10...to 11 at full brightness. The only use that I can imagine are the old blue sex lights that were all the rage in the '60s.

As you dim the dash lights, the sex lights dim too.

What other use would there be?
Over to you guys.