There is always a fix! Sounds as though you have a dead short, probably in that part of the harness that contains the glow plug wiring. My guess is that it has melted insulation off several of the wires in the cluster. Pick that section up and get a look at it all around. Cut the burned/melted section of the loom apart to determine the extent of the problem and then repair the wires as necessary. Be certain to use like sized wire for any replacement and insulated connectors for your splices. I usually use heat shrink tube over splices to keep any water out.

Good luck,
Jim

__________________
2005 C240 4matic wagon (daily driver)
87 190D - 225K (on loan)
85 190D - 312K (on loan)
2011 Subaru Legacy AWD (Wife's)