1983 240D A/C fuse problem.
 

My HVAC fan will run fine in either of the first two positions. When I dial it up to high speed, it melts the plastic fuse body. It has happened twice, both times with the 16A fuse. The first time it took a while (60-90 seconds) before the fuse melted and deformed enough to lose connection at which point the fan stopped. The next time it happened within a few seconds. Neither time did the fuse blow! The only reason the fan stopped both times was due to fuse deformation and loss of contact.
Any ideas?
Also, where can I get the ceramic bodied fuses? My local stores only have the plastic ones. Of course I need to fix a problem I might have before I put any of those non-melting fuses in.;)

Has your blower-motor fuse been replaced with the external one? My '83 240D has a burned out hole in the fuse box for the blower motor, and a nice OEM install (part of some recall, apparently) 30A strip fuse mounted on top of the driver's wheel well right near the A/C relays that has replaced its functionality.

I would start by looking at the blower motor and determining if it's dragging and causing high current. Does the blower make any noise (worn bearings). Mine works fine with the original fuse design.