Sounds like the gauge to me or the 12V to the gauge. The gauge is really nothing more than am ammeter that is measuring current. As the resistance of the sending unit varies (which is directly propotional to the oil pressure) so does the current. That said, you have 12V connected to one side of the gauge and the other side running to your sending unit. The fact that you didn't even get any deflection when grounding the lead at the sending unit would be one of three things: open circuit due to bad gauge, open wire or no 12V to the gauge.
Pull the gauge and put a 1.5V battery across the leads and see if it slowly deflects as it should. Also check for 12V feed to the gauge, and then finally continuity to the sending unit.
|