My old oil pressure gauge stopped working. Installed a new gauge and still nothing changed. I have 24v going through line 27 and 24v leaving the gauge to head to line 36 to the sending unit. Ran a new wire to the old sending unit and nothing changed. Installed a new sending unit now and the truck reads 50psi. When I Rev the engine the gauge bottoms out to 0 and then back to 50 psi. The gauge can't be wired up backwards and I have power coming to and from. Any thoughts on what's causing the issue? The gauge is grounded and still misbehaving. Any help would be greatly appreciated.