Cadillac Repair: 81 coupe de ville not charging, charging system, diodes

Question
replaced headlight switch on 81 coupe de ville, now the (no charge light) comes on and the battery goes dead. changed battery, at idle the charge light is off, above idle the charge light comes on, battery still not keeping a charge. please help.

Answer
WHY did you replace the headlight switch ?.

If you replaced it in trying to resolve your charging system problem the switch is NOT your problem.

The cause of your problem is that one of the 3 diodes within the bridge assembly of your alternator is faulty.