I had something interesting recently. I was driving my 1991 xjs and noticed that all my instruments were dead. Discovered that the switch on the gear selector for the back up lights had gone bad and was blowing the #4 fuse
The same fuse for the back up lights is the fuse for the instruments
Found an exact replacement from Terrys Jaguar parts $10 plus $10 shipping .........works great !

Now if only I could get the tachometer working ... it was not working before and not working now think I may need to add a ground