Hi Bill,
some of the capacitors were obviously bad. There was black residue from the electrolyte on the circuit board around some of the capacitors which indicates a clear failure. The electrolyte seems to spill out from there the leads enter the case and there is some bulging of the bottom of the capacitors that failed. However, capacitors can also fail simply by drifting or internal shorts and these failures will often leave no visual clues. Most of the capacitors that I replaced looked perfectly fine but I am sure that they were drifting considering how widespread failures in the speedometers seem to be.

I took a look at the fuel gauges that I have lying around I see several electrolytic capacitors but I have no idea if these are a problem. The 1992 gauge has quantity 3 of 47 uf 10v 85 degree capacitors, one 22 uf 25v 85 degree and one 220 uf 10v 85 degree capacitor. There are also 2 0.1 uf metal film capacitors. There are no signs of failure of any of the parts, and this was a working gauge, but the capacitors are suspiciously similar to the ones that I took out of the speedometer and with a lower temperature rating. If I were to replace these capacitors I would use 25V or higher units with a 105 degree temperature rating to prevent drift and shorting.

Mike