I got a pair of LED back up "bulbs" along with the other LEDs for my '85
automatic transmission Vanagon, and they are on all the time when ignition
is on (other bulbs work fine). The switch on the selector is brand new (both
parts), but there is a constant 5v at the backup lights and at the switched
contact on the selector switch, and the proper 12 volts on the power side.
5v is enough to illuminate the LEDs.

There has to be some kind of short in the wiring between the switch and the
lights, but where would that wire pick up 5 volts?  The rear taillight light
assemblies are in excellent condition and I've re-done the ground at the
left taillight.

I've had to go back to the filament bulbs until I can figure this one out.
Or maybe just forget about the LEDs because the short is probably buried
somewhere in the wrapped harness under the van.

No end to the fun!

Stuart