Gage malfunction

On My Focus 2000 I've been noticing that while driving sometimes my gages just swap to the max, down to zero and then back to normal. I just changed my alternator because i had a bad regulator, but the problem continues to come back..not as often like before. Does anybody have the same problem or maybe a clue to what it can be or what i can check? Thank you

sounds like a bad ground on the battery

A similar needle sweep on startup is also usually a sign of a battery on its way out in the Focus.