My '99 Century Has A When It Wants To Electrical Fault.

I was driving in the dark, literally, when the lights went went out. not just headlights either! All running/driving lights exterior, all cluster lights and switch lighting. I had just turned a corner and was able to stop quickly. So THAT's what my Wife was talking about. Following her remedy I flipped the dimmer switch, tilt and turn the steering, turned the ignition off and on and turned manual headlight switch on and off several times in random order. I had cluster lights but no headlights with manual switch. Flipped dimmer, YES, high lights! Flip some more, have both high and low now. Bad dimmer switch- got it fixed. Automatic headlight system still troubled.  I've found that other systems act up in sync with lights. Lets see. Auto lights, cruise, heater fan, dual temp controls, rw defrost and fuel guage. I checked and cleaned as many ground wires as found: some under dash near and on column, pass. side, under carpet, in trunk, under hood between body and engine, grounds to body and engine from harnesses. Don't have schematics to verify all. Checked all fuses and relays under hood and side of dash. Doesn't matter day or night, driving or still, restart engine maybe or not. Is there a control module that connects all of these? Suggestions any one?