Was your alternator checked on or off the car? If it was checked on the car did they try it with the head lights on? I had the same problem on my 78. It turned out to be a Worn And loose fan belt. (Don\'t laugh sometimes the most simple things are over looked.) Didn\'t feel that loose, but I Guess it was loose enough so it wouldn\'t handle the extra load from all the lights. It Never gave any indication that could be the problem.