[ray_mcavoy]

The printed circuits themselves are generally quite reliable. Problems usually tend to occur at the connection points and can often be repaired with a bit of cleaning.

In particular, look at the little metal clips that connect the printed circuit to the studs on the back of the gauge. Look for rust on the clips and/or corrosion on the printed circuit's copper where the clips make contact. If necessary, carefully snap the clips out of the holes, clean up the contact points, and snap them back in. To prevent future corrosion between the two metals, I like to use a little bit of conductive anti-oxidant compound (available in the electrical section of most hardware stores).

Also take a look at the cluster plug connection points. Look for damaged traces on the printed circuit where the plug's terminals make contact. Also look for bent or deformed terminals in the cluster plug that could be preventing a good connection.

Finally, there is a current limiting resistor on the back of the voltmeter itself. It's held in place by a couple of nuts. Make sure those nuts are secure (but not too tight or it'll crack the ceramic resistor substrate). It's rare, but those resistors can fail and cause the voltmeter to quit working. You can test it with a multimeter ... I think that resistor is close to 130Ω on most of these voltmeters.