Repairing Your Engine Wiring Harness

[umfetu]

Its not only the German car brands... Most car manufacturers that fall under the UN has this issue. the reason we in SA have the same issue as our American friends is because most of the American cars and parts comes from MBSA

[wbain]

Originally Posted by cjshade

Albert,

The wiring Harness issue (from what I have read) was a mandate by the German Govt. to use biodegratable wiring harnesses and other parts too. The insulation was not tested for long enough a period before the German auto makers were forced to use it. By the time the rapid degradation was discovered, the damage was done. I understand M/B was not the only car line affected. I think I will try and do some deeper research and see if I can find the truth. If I suddenly dissapear you know they got me!

Good Luck and Welcome to the Forum!

C as in 220

Volvo had this same wiring harness issue back in the mid 80's. My 1986 740 Turbo had the same wiring harness problem and I had to replace it. Not that hard really, but it was expensive.

[doin12volt]

Originally Posted by tommann

My final thought is that I am discouraged that this $730 wiring harness is really the tip of the iceberg. The new harness replaces everything with an end connection, but the opposite side of wire-to-wire connectors have the same insulation degradation issue as the harness. It would seem that eventually, things will short out, and every wire in the vehicle will eventually need to be replaced.

Eventualy yes, but probably not in our lifetimes... I work on these cars all the time.. ( I also rebuild W202 engine compartment harnesses...) It is the harsh engine compartment temperatures that makes the insulation kick into "overdrive" in the biodegrading arena.

Since the passenger compartment is mostly sealed from the elements, (as well as any othe car) and has a lot less heat,the wires behave differently. I have noticed that the wiring in the doors and underdash areas, along with the trunk, seems to stay quite supple and pliable. i have yet to find a degraded or even "brittle" wire in the passenger compartment or trunk to date, so dont worry too much, we can all breathe a small sigh of relief.

Fix your engine compartment wiring, kick back, admire your work and have a cold beer... your w202 will be with you for quite a long time.

[M104-AMG]

Originally Posted by doin12volt

<SNIP>

Since the passenger compartment is mostly sealed from the elements, (as well as any othe car) and has a lot less heat,the wires behave differently. I have noticed that the wiring in the doors and underdash areas, along with the trunk, seems to stay quite supple and pliable. i have yet to find a degraded or even "brittle" wire in the passenger compartment or trunk to date, so dont worry too much, we can all breathe a small sigh of relief.

<SNIP>

I have three W124's: 1988, 1993, and 1995

ALL passenger compartment area wiring is subject to bio-degredation and cracks in the insulation.

It took 20-years for the 1988 W124 wagon wiring in the lift-gate to fail; the 1993 500E passenger door and HVAC wiring had cracks in 13-years; and the 1995 E320 wagon took 13 years again for the lift-gate wiring to go bad.

My 1978 Dodge Van (1-owner!):
original engine & interior wiring with only a splice for the failed alternator B+ wiring.

[doin12volt]

Well, I have been thru MANY benzes, under dashes, in doors, floorboards, trunks, and have NEVER seen any biodegrading wire anywhere besides in the engine compartment.. I have been doing automotive electrical for the last 17 years as well... so take it for what it is worth, Like i said - ALL the wiring WILL fail one day, but it will last A LOT longer in the passenger compartment.

[infoage1]

fyi, for those that reference my web site concerning this manufacturer's defect:

I have changed servers and the new web site is listed below.

Also, that I have updated the reported NHTSA complaints to well over five-hundred to date. Among the new complaints are over a dozen (new) fires, and an accident. Also, a very large number of new 1996 complaints, and a some more 1991 complaints:

Mercedes-Benz 1991-1996 Engine Wiring Harness Defect NHTSA Complaints Summary

Mercedes-Benz 1991-1996 Engine Wiring Harness Defect NHTSA Complaints Summary Images

[lovemyc280]

Aside from the main engine wiring harness, how many other harnesses are inside the engine bay? Do they all need to be replaced eventually?

[doin12volt]

that seems to be a matter of opinion more or less, but the main harness in the engine compartment is the major problem.

[jbennett]

I fixed my girlfriend's juvenile delinquent daughter's 94 C280 by peeling back the black jacketing around the wires going to the coils. I found that there was NO insulation on any of the wires and they were totally bare. The car will at least run now. It wouldnt even start before I separated the wires. My question is how is the best way to repair this section of the wiring? There is a lot of molded rubber on these wires. Does the insulation typically deteriorate under all of that rubber too? I didn't strip it back. The problem I am having is up inside the end of the connectors where it is difficult to get tape in or to keep the wires separated. All help is appreciated.

Jeff

[Gary Weisbrod]

Originally Posted by doin12volt

that seems to be a matter of opinion more or less, but the main harness in the engine compartment is the major problem.

I'm sure you get tired of wiring questions, hope you have patience for one more. I have a 600SL all of the wiring was bad under the hood. I tried to skip the throttle body harness, but it looses it's mind and goes into "limp home" about 5 times in a 3 mile trip. So I am replacing the last harness now. I have had the throttle bodies rewired by 4Mercedes and they checked out the computers and tell me they are ok, so here's hoping! If you have any other suggestions I would appreciate it.
Gary