Passat Tailgate Won't Open: Troubleshooting & Repair

Hello,

The vehicle is a 1998 3B variant.
Problem: The tailgate will not open. The lock mechanism for manual opening with the key is severely corroded and stuck, although the actuator itself seems to be working.
I've already tried having someone operate the release lever while I kicked it from the inside, but without success .

You can't access it from the outside, and there are no maintenance covers inside, nor any lights installed that can be replaced from within. To reach the third brake light, you need to remove the interior trim panel while the tailgate is open.

Does anyone have any advice? I don't want to destroy anything if it's not absolutely necessary .

First, the simplest approach: apply plenty of rust remover around and inside the lock cylinder.
Perhaps you'll get lucky and the cylinder will eventually move again.

Could it be that the 3BG is about to be released, or is the 3B still mechanically driven?
If that's the case, you can try the following:
Remove the rubber strip on the outside of the button for the tailgate and pull the lever back slightly.
The rocker switch is becoming difficult to operate and keeps the button in the "on" position until it can't go any further.
Good luck!

"Edit:"
Okay, I'm ready. Please provide the German text you want me to translate into English. Just paste it here, and I will give you the translation.

The operation of the 3B5 is still purely mechanical.

Before attempting to remove the trim piece, try spraying it with a rust remover like WD-40 from the outside. This has worked in the past and might save you the trouble of fiddling with the trim inside the trunk.

Quote:

Before attempting to remove the trim, try using a rust remover like WD40 from the outside first... it has worked several times before and might save you the hassle of dealing with the trim inside the trunk.

I've now completely soaked it in rust remover – let's see if that makes a difference...