I searched and found all kinds of threads on how to upgrade to an LED bulb, but nothing on where this is located. I have a parts car and I went out to remove it and it wasn't obvious where it was. Any help? Picture? Diagram?

Under the ski slope just aft of the gear shift assembly

Cheers
DD

(';')

Thank You. So, I have to remove the shifter cover to get at it?

Yes. You might even need to remove window switches from the panel and set the whole thing aside to get there.
The 2 halves of the Opticell might be a bit stubborn to get apart if it's been some years. Care is needed with that as the mirroring finish is on the Outside! (Whose bright idea was that??) They merely twist apart about 1/4 turn.

You probably don't need to be told but the next person who reads this might, one Must be careful of the Optical Cables when messing around with this. If the fibers are crushed, light transfer will be compromised or destroyed.
(';')

in the Series 3 you don't have to remove the shifter at all.

if you just want to replace the Bulb, then you remove the console Lid and plastic tray.

There is access to pull the bulb holder from behind the opticell casing through the bottom. The bulb holder has two wires, one is Red, the other is Black.
to remove the bulb holder, you need to push it to one side, whether north or east or west.

to add to my comment above:

push and pull the silver color bulb holder to one side or the other, it fits into the opticell back with "spring" tangs so it may be stuck. Do not pull on the two wires.

Use a bright lamp to find it, it is located to the left side of the rear of the shifter. Can't miss it.

I found its location, unfortunately someone had already removed it. At least now I know where it is.

what had been removed ? The opticell case or the bulb holder ?

Someone here a few years ago found a way to put tiny LEDs in place of the light pipes behind the instruments.
Is that what's been done to your car?
I can't see any other reason to totally Remove the Opticell, as that leaves all those things DARK!!
(';')

The car is a parts car and somebody had already removed the whole Opticell. I can understand the thoughts on using fiber optic cable, but it doesn't make for very bright instruments. I have the same issues with my W123 (1985) Mercedes as they used the same thing. I can live with it for now but have been doing a lot of research on using LEDs to make things a bit brighter.

the opticell system can be bright enough, WHEN SET UP RIGHT.

when the normal incandescent bulb is replaced with a higher watt incandescent bulb, the tips of the cables inserted at the opticell case get charred and transmit less light. Then maintenance is required, each cable tip must be pulled from the case and sanded smooth, removing the burned crust from the tip.

Then a bright, forward projecting LED does the job.

Also I have learned that not all the positions at the case where the cables are inserted, provide the same illumination, some positions are dimmer than others, and those positions were used only in the Vanden Plas cars that have more indicators to illuminate. Takes some experimentation in a dark garage to find the really bright positions.

I looked into using individual LEDs but it was too complex dealing with resistors and soldering, as if the mess of optic cables was not enough

The solution is to project a powerful light from the rear of the opticell case (where the bulb socket snaps into place), towards the cable tips.
You can see this result by pressing a small powerful flashlight from the rear of the opticell into the bulb socket opening. You can also see how the illumination changes by rotating the flashlight in small increments. Weird.

So why does a flashlight resolve the issue ? It must be the LED forward-projecting bulb.

For my 1984 XJ-6, I asked Mike Eck of www.jaguarclock.com fame to build me a solution.
He did a printed circuit board with 7 LEDs and by golly the indicators lighted up like Christmas lights!
But don't ask Mike to do another one, he said it was too time consuming. I got really lucky. Mike is a wizard with electronics, owner of two Jags.

Contact David for a opticell unit with cables if you are missing yours. It is a simple system.

Higher wattage incandescent bulbs mean higher lumens, but also a lot more heat is generated and like said, that is not good for the tips of the fiber optics. With incandescent bulbs only 10% of the energy turned into visible light with the other 90% nothing more than heat. That is one of the major benefits of LEDs, less heat for the number of lumens produced.