I checked through the forums but didn't locate anything quite like my problem with my turn signals on my W124 (1994 E320 Cabriolet).

It seems when the humidity goes up, the turn signals go out. They'll work for a while ... then slow down and stop altogether. This began last summer. I replaced the turn signal stalk (combo switch and the problem disappeared for a few weeks, then began again. I reset the Hazard switch and, over winter, everything worked fine. But now that summer is here, the problem is back. The forums suggested the Hazard switch was the problem, so I recently replaced it. For a few days, all was OK ... but now the problem has recurred. This is maddening!

I can get the signals working by pushing the windshield washer stem on the stalk; the indicator will come on and will work for awhile. But eventually, they conk out. Can anyone help me with this gremlin (other than just driving in the winter)?

Sounds like a bad ground point.

W124 Turn Signals -- Success at Last!
http://www.peachparts.com/shopforum/tech-help/101644-how-do-i-replace-combination-switch.html#post1300184