I just replaced the fiber optic bulb on my 1989 XJS with a bright LED bulb. The LED did nothing for my switches and rockers, Any ideas what to do; How difficult to respace the fiber optics

 

I replaced my feeble, archaic incandescent bulb with a 5-unit LED:

Lit them right up, it did! I can see then all easily.
(';')

 

Are you sure the fiber optic lines are intact?

 

When you have that bulb out it's worth shining a bright flashlight into each optic filament when it's dark to see if you're getting light transmission through them. It's a flawed design and get's even worse with a lot of
other bulbs as the light really needs to go into the optic guide at a good angle and brightness it seems. If you fiddle with them with a flashlight you'll see how finicky they are.
Some positions on the fiber holder seem to work better than others too, you can pop them out and move them around to light up what's important to you. I replaced most of my
hvac control panel ones with weeee tiny little rice grain sized incandescent bulbs and they work very well. The fiber still lights up the headlight switch and something else quite well
with just a good incan bulb and picking the most useful spot in the fiber holder since it had open spaces now.