Rain sensing wipers don't work?

[slowlanemcvane]

Okay, this one is a serious annoyance to me. My E70 rain sensing wipers don't work. I live in sunny Western Washington, the drizzle capital of North America. Thanks to the presence of rain sensing wipers, my car doesn't have an intermittent wiper setting, so it's either off, low-constant, or high-constant, or I constantly have to "bump" the wiper stalk to get a single up-down cycle. Thanks, also, to the unending drizzle where it seldom "rains" even the low-speed wiper setting is too fast, and causes the wiper blades to streak-skip-squeak across a relatively dry windshield. They worked when I first bought the car used a couple of years ago.

I have tried keeping the car running with intermittent wipers turned on, and spraying the windshield with a stream of water from a garden hose, but to no avail. The wipers simply do not work in auto mode. This wouldn't really bother me, except that there is no automatic intermittent setting like I have had on every other vehicle that I have ever owned, to include some really crappy 1990s American cars.

Is there a troubleshooting method that I should be using? Very few people post about this problem on X5s.