Cadillac Repair: 1989 SEDAN DE VILLE, chassis grounds, battary

Question
MY DIDIGATAL DASH LITES AND HEADLITES GO OFF & ON WHILE DRIVING. THIS HAPPENS SEVER TIMES FOR A FEW SECONDS AND THEN        COME BACK ON. THIS     HAS HAPPENED SEVERAL TIMES AND THE CAR STAY RUNNIN. SOME DAYS IT DOESN,T HAPPEN. I HAD RHE ALRENATOR REPLASED AND THE BATTARY CHECKED, BUT ITS HAPPENED AGAIN. THE CAR HAS 63600 MILES ON THE CAR.

Answer
Richard,
Wish I could tell you this would be a simple issue to diagnose but I can't. Intermittent issues, especially electrical ones tend to be a hit and miss type of thing. The first thing I would check is the main harness connections under the dash. The ones at the bottom of the steering column tend to be weak points on those cars, as does the battery cable connections, and body & chassis grounds.
Ultimately, it will only be luck or persistence that will pay off for you though. Hooking up test lights etc. to certain circuits at certain connection points can yield good results in that you can monitor the connection while driving by watching the light. You simply move through the circuits monitoring connection points until you nail-down the break point.
Looking at the schematics don't immediately show me anything on your car. The systems affected have a good deal of related circuitry that may prove to be daunting to trouble-shoot. If you want, feel free to send me an email and I can send you a copy of the schematics involved for your reference. Katshot@yahoo.com