So my 2003 sundancer 300 tach's are jumping. If I tap on them they will jump, also when the engines have just started. I have pulled the bezel and checked the connections and they seem tight. I don't see a switch on the back to change any settings like I have read on other posts. if I move the plug on the back of the gauge I can get it to move as well. Is it an internal problem? Can I service the gauge myself? Thoughts?