Wiring Harness
 

Does anyone know the symptoms of a failing wiring harness for a mercedes vehicle?

Thanks

smoke, intermitent electrical problem, dead battery for no aparent reason, switches that don't work, ect. ect.

You don't say what model you have but most wiring harnesses fail near the heat of the engine, for example as they go under the spark plug cover on a 104 motor. This causes misfires, rough idle or perhaps even inability to start. You will often get eratic and inexplicable fault codes. Sometimes touching the harness somewhere will cause it to run better or worse. But if you see crumbling insulation you're ready for a new one regardless of whether it's causing performance problems - unless you want to risk getting stranded.

1995 or earlier are the years in question. You have to visually examine the insulation. You will need to carefully cut open the protective sheating to see the insulation. Be careful not to hit the wires inside. See attached pics for examples. These are wires for the Hot Wire Mass Air Flow Sensors. My Electronic Actuator wires looked about the same. Injector wires are also suspect.

Thanks guys,

i own a 95 C280.

is there anyway to disable the security alarm feature on my 95 C280? and still drive the car as normal?

You probably need to start a new thread on this but I have certainly disabled the alarm system on E classes of that era. There is an alarm module under the front passenger footwell, remove carpet, etc, disconnect the alarm, take it in the house and the alarm will never go off again.

Just to supplement other comments, the best sign of a failing wiring harness is "never been replaced, original equipment". In the early 1990's DaimlerBenz chose a supplier who used degradable harness components. To put it plainly, the wiring harnesses were designed to fail after an unspecified number of years in the hot engine compartment. The M119-laden cars are more prone to complete harness failure (for obvious thermal reasons).

It is a good idea to do this before you experience symptoms. One forum member had the harness in his 95 C280 short out the throttle actuator and control modules a couple years ago. Repair bill was in excess of $4k USD. Should be substantially less as a preventative maintenance item, especially if you do it yourself.

-DM

Do you have an estimate of what the price the dealer charges to change the wiring harness?

Also, if one was to do this job by them selves, about how many hours will this take?

Thanks

I believe the harness is priced around $600 and labor is about 4.5 hrs. Factor a dealer labor rate at $90-120/hr. and that would be your cost.

This fix was goodwill'ed for cars with less than 100K miles, but I don't know if the dealers still honor that.

I've heard of dealers charging six hours for it on a 104 motor. I've also heard of it being witnessed done in an hour and 15 mintues. I did my 104 motor in less than 4 hours with no prior experience and working a snail's pace. It does make sense to work carefully but you pretty much can't screw it up.

Guys on my 95 C280,

The HTT/ or computer they used (i forgot the brand name) has indicated that there are "faults in the door circuit" but when wanted to extract the details, it states undefined.

Could it be that there are faulty wirings (or other possbilities) in the doors circuit be related/ connected to the rear view mirror and causing my intermittent starting failures (red & green lights flashing)?

What year was your car? The DIY shows a model with the battery in the engine compartment. My 94 c280 has the battery in the trunk. So, while I'm pretty top notch on DIY, I'm wondering what kind of wire pulling/routing problems I'll face with getting the new harness installed.

Advice?

Is the wiring harness problem only related to the engine harness, or were other wring harness’ within the car made of the same biodegradable stuff?

Thanks,

BDBENZ

As in all these posts, when I read them I get a bad feeling in my stomach,,, look at my sig. So tonight, just for kicks, I pulled some wires apart that run right on the engine on my 104. The wires are as pliable as new. Go figure. My parts person at the Benz dealership where we get all our body parts says he gets calls for one about every two months, and agreed with me that with all those cars out there, he is surprised he hasn't gotten more. He also said he hasn't sold one for a 119 engine yet. The price for the 104 harness is around $500.

Pete,

Let's hope you got lucky! I had to replace mine; another member who also has a '93 like you, hasn't had any trouble either. Both of you have about the same miles on the clock, so I don't know for sure if occur in the future or not.

btw... my replacement harness was made by Delphi.