[Buzz]

Update. Just to satisfy myself that the problem wasn't in the wiring harness between the dash and the sender, I disconnected the signal and ground wires from the gauge and ran jumper wires directly between gauge and sender. Same symptoms. The only constant is the positive lead to the gauge. All other gauges are fine. I did notice however that the needle also jumps a bit when I turn on the windshield wipers. It still remained unresponsive with the ignition on and lights off. I think I will order a new gauge and sender along with a voltage stabilizer and see what happens.
PS; I drove around quite a bit last night with the lights on and no problems with the fuse - fixing up my grounds seems to have worked, but should I still install a relay?