Just got car back from garage, had same erratic wipers, don't come on often enough when its raining, go mental when there is not a cloud in the sky. They couldn't replicate this and so I'm obviously imagining it. Put car alongside a VW passat with auto wipers and the VW went off three or four times more often than mine,(it was raining at the time). I have also found that on a really bright day with deep shadows across the roads, the shadows will always set off the wipers, without fail. The sensor is linked to the auto lights too, but they seem fine at the moment. This is the second Ford I've had and I wouldn't get another. Designed to look good, but underneath just the same old crappy ford workmanship.