Dodgy Wiring in Car

My fuel gauge needle just went to the bottom for no reason.  I was sure it was a quarter full earlier.  I worried someone tapped my tank and I had a vandalised tank to patch and wishing I have enough fuel to creep to a garage.  I drove on a little longer, and the needle creeped back up.  Steve reckoned there is a dodgy joint, causing high resistance.  Anyway, I need to keep resetting the odometer to double check my actual fuel level.