Today, the wiper on my 10 year old c180 started stuttering across the windscreen during heavy rain... It came and went that way for about 30 minutes, then there was a 'pop' and the arm started wiping again.

However, it now simply wipes in a crescent shape, it should wipe in a sort of 'cam operated' up and down crescent shape.
Because of this, the wiper now hits the front windscreen pillars at the full extent of the right and left wipe.

The wiper arm can now also be pushed in and out.

I haven't had a proper look (to dark and wet) but has the wiper arm popped off part of the driver shaft or whatever? Is this fixable? is it easy/cheap to fix?

thanks for any guidance

The covers come off with hand pressure. Search the DIY links for the procedure to lubricate this mechanism, which includes removing the covers. I am betting that you won't like what you see.

When you get a new one on there, lubricate it once in a while to prevent this from recurring.

hi thanks for replying.

Ive taken the covers off and greased as required - hey presto I now have some 'up and down' movement again...

However,
on re-assembly, my wiper now seems to have no 'synch'...
It sometimes sweeps fine, other times it pops up and down in the wrong places making it still on occassion hit the windsreen side pillars.

How do I resynch the mechanism so it pops up and down as required during the sweep, or is this a sign something is seriously wrong under the part I lubed?

There's something seriously wrong under there. I believe that there's a set of gears in there somewhere (I haven't dismantled my 210 wiper far enough to see them). Sounds like yours are bad.