Thanks for the input so far. I will try those ideas tonight. One other thing, though. As I was driving the car last night, I noticed that when I flip the turn signal on, the ammeter gauge pulsates right along with the turn signal. Do I need to ground the gauge somehow? The cluster itself is grounded by the wire just above the high beam indicator light.

Also, the gauge was on the discharge side the whole time I was driving it. Is there a way to test the alternator?