No intermittent wipers (16 E350 wagon)
 

The windshield wipers in my W212 wagon do not work on either intermittent setting. As I understand it, this could be the result of a bad sensor up by the mirror, or it could be a bad relay.

How do I determine which issue I have? Also, which relay is involved (I have not yet figured this out looking at fuse box diagrams)?

Thanks!

Just to wrap up:

I had a suggestion from somewhere else to pull the F10 fuse and the L relay for a few minutes, then reseat them and check for results.

I pulled the fuse and relay for 4-5 minutes. Once the hood was closed tightly, the wipers would activate on intermittent when I sprayed water over the sensor. I call that victory!