When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
It's the switch! I had the same problem.
Pound or hit the switch...push it back and forth and you might be able to get it to work...then you'll have to replace. There was a TSB on this.
My left rear window on my ML320 rolls down by itself. I can roll it up using the switch and it will stay for a while but it will eventually creep back down again.