Windscreen sensor problems

[idlerider]

Some time ago I reported that my windscreen wipers had defaulted to intermittant when set to 'automatic' and similarly, the headlights had defaulted to on when also set to automatic. The windscreen sensor and ribbon cable were replaced, to no effect. Now, things have gone a stage further: the headlights now remain on whatever the lighting switch is set to.
It has me beat, so if anyone has any ideas, I'd be very pleased to hear them!