Ammeter to Voltmeter...who does it?

the 1980's pickups [1981 to 1993 ?] used a shunt type system. Most of the current goes into the harness and only a very small amount goes thru the ammeter. It's a good system. My late 80's D-150 didn't work so I pulled the instrument panel out and found corrosion under the ammeter nuts. Used toothbrush style wire brush on the circuit board and nuts. A dab of grease on the nuts. Checked and greased the pins and both plugs. Checked light bulbs. Its been fine ever since.