Hi,

Welcome to the forum. I did a search on 'overheating 190e' and came up with this:
http://www.peachparts.com/shopforum/search.php?searchid=871438

I think the aux fan on your 190e is controlled by a relay that is screwed into the thermostat housing at the front of the engine. There may be more than one, and i'm not sure which one is the aux. Once you know which plug is the aux fan, you can test it with a multimiter and measure the resistance at different temps. If the resitance doesn't match up with what it should be, the relay is junk and needs to be replaced. If the relay checks out, hook the fan up to a 12v supply and see if the fan is ok.

Hope all of this is correct...its been a while since i looked at fans.

cheers,
dan r.