When my truck is idling, the needle on the amp meter gets buried to the right. When I turn the lights on, they flicker or blink intermittently. As this is happening, the needle on the amp meter bounces up and down in rhythm with the disco lights. I have replaced the battery and the alternator. Actually, the battery was replaced a while ago, but then I ran into this issue of an alternator with an open diode, which kept killing the battery. So, now, I have replaced the alternator. When I picked up the new alternator, I had the battery tested and was told that it was good. I am electrically challenged, so I am not sure what might be causing this, or what I should be checking. Anyone have any ideas?