Finally! And, it was a real "duh!"
The bottom of the hood switch (near battery) had simply fallen off. It looked like the switch base (holds spring and pin) should snap back in to the top keeper portion ... appeared to simply be too loose to do so.
Glued it back together with superglue.
Seems to work 4.0.
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg