The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - How do the voltmeters work in these trucks?

ray_mcavoy · 12-30-2018, 07:00 PM

The voltmeters have a current limiting resistor ... it's the rectangular white ceramic piece on the back with a patch of paint in the center.

One terminal serves as the +V input. It connects directly to one side of the resistor and has no internal connection to the meter movement. The 2nd terminal serves as a connection point between the other side of the resistor and the meter movement coil. This terminal has no external connection to the cluster. And the 3rd terminal is the ground for the meter coil.

I don't think I've ever seen one of these clusters with BOTH a voltmeter and a battery light ... they usually have just one or the other. Although wiring diagrams will sometimes lump both together (often using dotted or dashed lines to indicate optional wiring) so you have to look carefully when following those circuits. The battery light (when used) typically has one side of the bulb connected to power via the ignition switch and the other side connected to the alternator's voltage regulator.

12-30-2018, 07:00 PM	#2
ray_mcavoy Registered User Join Date: Nov 2009 Location: Sherman, ME Posts: 2,373	Re: How do the voltmeters work in these trucks? The voltmeters have a current limiting resistor ... it's the rectangular white ceramic piece on the back with a patch of paint in the center. One terminal serves as the +V input. It connects directly to one side of the resistor and has no internal connection to the meter movement. The 2nd terminal serves as a connection point between the other side of the resistor and the meter movement coil. This terminal has no external connection to the cluster. And the 3rd terminal is the ground for the meter coil. I don't think I've ever seen one of these clusters with BOTH a voltmeter and a battery light ... they usually have just one or the other. Although wiring diagrams will sometimes lump both together (often using dotted or dashed lines to indicate optional wiring) so you have to look carefully when following those circuits. The battery light (when used) typically has one side of the bulb connected to power via the ignition switch and the other side connected to the alternator's voltage regulator.