Rally dash oil pressure gauge issue.

Yes I have oil pressure verified with Snap on mechanics gauge. 45 at idle 55 at 2000 rpm. I did the inline resistor test with a 10 ohm resistor. The oil gauge went to what would be just under half on the gauge, or what would be a quarter tank on a fuel gauge. I also have pulsing voltage on my test light. At this point I am thinking it's the sending unit or a bad ground on the sending unit. It is new and I think it had thread sealer on it. I am going to pull it and take a second look.