Ammeter Problems/Questions
Here's an awesome article about this very issue:
I wouldn't put it back together till you read it.
http://www.madelectrical.com/electricaltech/amp-gauges.shtml
It discusses the problem and tells how to implement a solution. I'd run a voltmeter if the car gets driven a lot. I wouldn't do anything till you either perform the fix or figure out the problem or you'll probably smoke the gauge again.
Good luck!
Steve