Fried wire in the fuse box
 

I've got a 1993 300TD and it didn't start today in the cold. The glow plug light didn't even turn on. Came back this evening after work and popped the hood and first looked at the fuses and looked no further as a red wire running along the inside edge of the fuses (within the box) was cooked. Obliterated. It burned up most of the paper fuse diagram that sits under the box cover as well. Some fuses below this wire are black but otherwise look OK. I'm guessing this wire is my issue with the glow plugs...although all other electrical components of the car work even with this fried wire.

The red wire is severed in two from the burn...but it looks like it was connected to itself by some sort of fuse as well. Whatever fuse was there is gone/melted but there is a rubber boot, that didn't fully burn, which likely held this fuse.

So I'm wondering:
1) what was there exactly at that red wire connection?
2) is there a source for a fuse diagram so I can see if the correct fuses are being used?
3) is that red wire a connection for the glow plugs...and if so would a faulty glow plug cause such a reaction?

Thanks guys!

A picture would be of interest.

You will find a wiring diagram at this link

Hmm it didn't let me post the link. Try searching
Model 124 Maintenance Manual Index

In the 1982-85 M-B, the #8 fuse position often melts the plastic from the high current of "blower high", which happened in my 1985. I measured high voltage drop across a crimped connection below that fuseholder, so soldered across the crimped pieces. My 1984 doesn't have that crimp, but I did the same pre-emptive fix in both cars, which was to run a thick wire straight from BAT+ to the blower speed box (above glovebox liner), with a 30A relay actuated by the OE +12 V feed wire to that box. In the fuse-box I had to solder in an inline fuse-holder since the plastic was too melted to use the OE copper holders there.

Thanks for the replies!

I just got a photo in the snow and dwindling light of the fuse box and the thicker red wire with partially melted rubber "boot" on ring finger and where it connected to a thinner red/white wire on index finger. I cleaned the melted garbage off 3 of the blackened fuses below the burned former connection and everything seems to work well...with the exception of the glow plugs. No other evident electrical issues.

Maybe this has nothing to do with the glow plugs...but it sure as hell goes to something! :) And the blower/fan still works too.

Tomorrow in the daylight I'll check each of the five glow plugs at the relay.

Hmmm.

sir, I had the same problem with my 617.951, I unscrewed fuse box so I could see any damage, when raise up. I figured maybe too many glow start cycle's. I then cut out damaged section, and used a larger grade of wire. spliced, and soldered