1995 Buick Skylark - rear electrical problem when cold

My 1995 Buick skylark has been experiencing an electrical gremlin of sorts that can't be located in the shop. When cold outside (below55 degrees), USING LIGHTS. It won't turn on dash board lites, won't "ding. Ding" alarm warn me when I exit car with headlights still on, and I have no rear running lights. My headlights and brake lights and emergency flashers work fine. NO ENGINE LIGHTS OR CODES ARE SHOWING UP?
But when it is over 55 degrees outside, all of these "problems" go away.
I assume I have a cracked wire or loose module or loose terminal or post, but am frustrated in the search process. Looking for answers on where to look. Looking for wiring schematic to be help pinpoint / trace