Electrical Fire Under The Hood - PeachParts Mercedes-Benz Forum

lsmalley · #1 03-10-2014, 01:19 PM

Today as I was exiting the freeway I noticed a burning smell and saw a thick plume of smoke coming from under the driver side hood. Once I was clear enough to pull off to the side and lift the hood I noticed the thick cluster of electrical wires running along the driver side up to the fuse box were ablaze. Shut the engine off and had no choice but to throw water on it to put it out. Right when I smelled the smoke is when the instrument cluster died, driving lights shut off, radio went off, and automatic start shut off. 6 fuses had blown as a result of the fire fusing the wires together. I was still able to drive to a safe location (my grandmother's house) to access the damage. Pretty much the entire wiring loom on the driver side was melted all the way down to the pre-resistor next to the ABS unit. It took me well over 8 hours to clear all the charred plastic and reconnect the wires, not how I planned on spending my sunday vist with grandma. I was able to get everything back together and replace all the fuses to make it back home, but I will definately be sourcing a wiring harness from a junk yard as soon as I get a chance. As for the cause of the fire....seized bearings on the auxillary fan! I should've known as I turned the fan on earlier today and heard the whirring-squeaking noise of the fan, didn't think much of it....Matter of fact, didn't know what had caused the fire untill I got everything back together, but I did trace the origin of the fire as starting on the pre-resistor below the ABS unit. I just thought that there was a short on the auxillary fan because the fire seemed to had either bean at the pre-resistor or the actuall driver side aux plug. Once I had everything back together I randomly tried to spin my driver side aux fan by hand and it was stiff

. The passenger side was fine. At that point I knew what caused the fire. Pulled the #3 Fuse for aux fans and disconnected the fan. So I will also be picking one of those up from the junk yard as well. Lesson: nake sure to pay attention to bad bearings!

pawoSD · #2 03-10-2014, 01:22 PM

Yikes!! Did it not blow the fuses for the aux fan? It has fuses....

lsmalley · #3 03-10-2014, 01:27 PM

Yes, it did. But I'm also wondering if the manual aux fan switch in the cabin played a part in this. Which would be weird, because that is wired through a relay and as also fused. I've only experienced something like this with bad bearings one other time and it was when my air pump seized up and charred my fan belt.

pawoSD · #4 03-10-2014, 02:18 PM

Manual aux fan switch? Is that an aftermarket addon? I did that on my 190d, however I just jumpered a switch to the sensor on the A/C system receiver/dryer, so I am essentially just "triggering" my fan through the stock relay, its not an actual power switch or powered line to/from the switch. Works very well....

lsmalley · #5 03-10-2014, 03:56 PM

Quote:

Originally Posted by pawoSD

Manual aux fan switch? Is that an aftermarket addon? I did that on my 190d, however I just jumpered a switch to the sensor on the A/C system receiver/dryer, so I am essentially just "triggering" my fan through the stock relay, its not an actual power switch or powered line to/from the switch. Works very well....

Not after market, just rewiring the aux fan wires through a relay and then to a switch inside the cabin. I used the center vent, which my car has 3 spaces, but only uses 2, so I moved the switch on the far right to the center and added in a switch for the fan. I used a rear dome light switch and just flipped it upside down to avoid confusion, although the rear dome light switch is actually on the driver side vent.