Problem with Rain Sensor on CLK
 

I have a CLK and recently had to have the Windscreen changed by a windscreen company. When they had changed the Screen I found that the rain sensor was not functioning properly.
On contacting the windscreen company - they told me that by accident they had unplugged the moisture sensor and now it would have to be re programmed by Mercedes Benz - Is this true ?
Basically the sensor does not detect rain fall very well now ?
What is the best way to check and correct the problem ?

I'm afraid they are correct! Someone with *star-diagnosis* lap-top should be able to help as long as the rain sensor hasn't been damaged.