I had the same problem with mine.  You can remove the 2 wires that go to the
switch and connect them together which would simulate the switch working.
If it's just a bad switch, the lights should light.

I ordered a new switch and while I was waiting for it to come in I removed
the old switch and cleaned it really well by squirting Ronsonol lighter
fluid (Naphtha) alongside the plunger and working it repeatedly ... soaking
up the black stuff that washed out of it with a paper towel until it showed
clean.  After it dried, I lubed it and reinstalled.  It worked (and still
works after a year) and I just put the new one on my spares shelf.

Mike

About 2 months into my ownership of an '88 GL Wolfsburg / Manual trans. and
just noticed the other night that my reverse lights don't work.  Replaced
all bulbs and checked all fuses and still no luck.  I've heard of a reverse
switch that is actuated by the shifter but can't seem to find in Bentley
much reference to checking or just plain replacing this switch.  Anyone else
had similar experience?  Am I jumping the gun by replacing the switch?

Thanks
Barrett
'88 GL Wolfsburg
'87 A2 GTI 8V