Check the fuse before you do surgery. The blower motor itself might just need a little lubrication. It happened to me. It was intermittent, then it stopped working completely. Removed the motor, lubed it real good and I haven't had a problem since. Works like new.

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1995 E420 152k
1991 300D 2.5 348116 daily driver
1992 300E 2.6 196k-work in progress(head gasket)
2002 BMW 745Li 93k