I have a 2001 Ultra Classic. Recently the fuel gage needle starting twitching. Sometimes just a little but sometimes it moves down a quarter tank and back. It does it if the tank is full, empty, or in between. I've checked the ground wiring on the gage itself, the plug under the seat for the sending unit and all seems fine. Is there a test using a multi-meter or something where I could possibly pinpoint the problem. Please help!!!