I think the tach is driven by a signal from the alternator. The fuel and temp gauges are separate units that can be removed and replaced. I think most of the circuits are foil strips within the cluster unit which can be accessed by removing the back cover. I've had a few units apart over the years and have been able to locate and "patch" a problem or two.
thanks harry, i might also add that headlights are barely coming on but battery is showing 12.34 volts. do you know if
tractor runs on more than twelve. i hate to get into the cluster
if its a voltage problem.
Battery voltage should be more like 12.6 to 12.7 standing voltage when fully charged, and at least 13.8 when running. 14.2 to 14.8 is better, but no higher than 15. If you have 12.3 when running, you have a charging problem.