Pressing the defrost button will set the fan to blow as hard as possible regardless the switch setting. It is supposed to do so...
I think mercedes got tired of the one arm wiper system as well, since they changed back to the two arm wiper systems again. The one wiper system is well known for the poor visibility (it transports the dirt from the entire right to the left to the right, etc...I have never heard of winter wiper blades either.

greetingz,

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1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)