Adaptive Cruise control has never worked on my car, I managed to pick up a used radar unit for a few GBP on fleabay. It might work, or I might use it as a paperweight. Removing the old radar the problem was instantly obvious - the connector on the unit had corroded. I separated the harness connector from the connector on the unit and one of the pins completely disintegrated, jamming the socket in the harness connector. When I removed the screws holding the bulkhead connector to the radar unit they all sheared off. There's an O Ring seal between the connector and the face of the radar's diecast box. This wasn't seated correctly, its a mess. As I withdrew the Radar connector there seem to be only three pins, the two outer connections seem to be dummies (and the centre one was corroded and broke on withdrawal)

This is the back of the connector that is screwed to the diecast box. Seems to have only three connections., the middle one disintegrated as I withdrew the connector from the box

Oxide everywhere. The O ring wasn't in the seat

This is the fron of the radar box mounted connector. the leftmost of 5 pins is stuck in the wiring harness
. It could be that in fact those two outer pins have been completely lost to corrosion.

If indeed the outer pins aren't connected I can remove the unused pin from the new radar's connector and continue to use the existing harness (which has an outer socket jammed with a corroded pin). Otherwise I face a choice of sourcing and fitting a new harness or connector, if I can't find the same I'll probably make up a connector using chocolate strip and wire wrapping onto the radar unit.... not ideal but functional

 

. . . I took the connector off the new unit for comparison . . . of course all 5 pins are connected!