I just went to replace the Oxygen sensor on my 95 wagon, and upon pulling up the carpet noticed the actual problem: The wiring on the 3 hole female plug (running to the car) has deteriorated and the green wire has broken. I proceeded to replace the sensor, due to its age, but now need to reconnect it to the car.

My questions: Is it enough to find a new plug, strip the wires, and reconnect? Or should i seek to replace all the whole wire?

I insisted my dealer install a new wiring harness before I purchased the vehicle based on its history of failure. Does this deterioration problem apply to all the wiring in the vehicle?

I just replaced the engine wiring harness on my 93 300E due to deterioration of the wiring insulation which caused engine problems. Cost a little over $900 for the harness, and I installed it myself. I've heard that the deterioration is because MB used biodegradable insulation. Isn't that the most brilliant engineering design you've ever heard of? (note: I'm being sarcastic). I'm curious to know if all the other wires in the car are like this.

elnorte, obviously it would be best to replace the entire length of the failed wire if that's practical. You'd hate to have insulation failure on the same wire cause other problems under the dashboard.

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Fred Hoelzle

More likely than not that this vintage car [ 92-95] are going to slowly start showing wire insulation breakdown throughout the vehicle.
The first to show was the infamous engine harness.. that was accelerated failure and would most likely be due to under hood engine heat conditions.. Being bio-degradable insulation, it would make sense that they are all made of the same compounds and are degrading according to design time frame plans..looks like a matter of time ..sad..........wish their time frame was long enough to get some mileage out of the car...makes you wonder why you were so concerned in meticulously changing the oil and such....huh?????????

Should I just chase the wire up through the dash?

Or, Can anyone let me know what is the final destination is of the wire before I go back in? I'm thinking if I disconnect at the source I can use the old to fish in the new.

I don't think it's a foregone conclusion that all the wiring in the car is going to fail. The engine wiring harnesses came from a subcontractor in Sweden. Most of the wiring in the car was installed at the factory in Germany. You don't really say how it's deteriorated but if the insulation is crumbling to dust it would be wise to do the whole length. Seems doubtful though. The color coding is very good on these things but the best place to start is with the wiring diagram for the car - which is on the service CD.

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No, not a foregone conclusion, just an observation ..have been seeing signs of cracking beyond the engine harness.. time will tell.

I still cannot find a receptacle to replace the bad one running to the car. Can I hard wire this, or is it essential to leave the plug and receptacle intact.

This is rather disturbing! I paid $725 just for the engine wiring harness. Imagine what it would cost to replace the wiring and related components on the rest of the car - not to mention the labor! This is a near impossibility. I hate to think that all (or most) MBs made in 93-95 will effectively be junk in 20-30 years when the rest of the wiring harness issue catches up with the car. At the rate I drive, my car will only have 80,000 miles after 20 years on the road.... 110,000 miles after 30 years.

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95 E320 Cabriolet, 159K