The fuse should get warm but not hot. Clean the fuse contact points and see if that helps the fuse to run cooler. Also clean the junction box contacts (top of passenger fender W123), assuming you have one on W124, which is the feed to the glow plug fuse.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked