W123 rear defrost switch help needed
 

I'm trying to troubleshoot an issue with the defroster switch in my 83 300TD.

The rear defroster operates, and the light indicating that the defroster is on illuminates, but the switch does not do the courtesy glow like the other upper dash switches (when the headlights are switched on, it does not illuminate like the other switches).

I removed the switches to have a look and it only has one fiber-optic connection, whereas all the other switches have two connections. I see light coming through the fiber.

Does anyone have any ideas? Could the switch simply be bad?

Is this a new problem, or one that's been there for a while? IIRC, this switch should have two fibers in it.

Only the antenna switch gets 2 fibers since it has icons on the upper and lower half.

All the others get one fiber in the upper half only.

I would try cleaning the icons with a little rubbing alcohol and q-tips (gently). Then clean the ends of the fiber cables. Be sure to use a fresh dry q-tip to lift off the dissolved dirt and alcohol, don't let the alcohol evaporate on the surface or the dirt will still be there.

Finally put a fresh bulb in the spider and see if that helps.