Sometimes they work sometimes they dont (gauges)

[zach33]

1987 R10
When I first bought my truck the fuel gauge worked (w/ both tanks), the volt meter worked, the clock worked, but the engine temp gauge did not. After a couple hundred miles i started it up one day and they fuel gauge wasnt accurate (registered about 1/16 of a tank but was full),and the volt meter stopped working. The strange thing is that when this happened the engine temp gauge started working and the volt meter stopped working. The only gauge that has continued to work is speedo and at this point im not even sure that it is accurate. Does anybody have any ideas?