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Oct 13, 2023

Mercedes-Benz parts supplier in the 90s used environment-friendly wiring harnesses that made it wither away. And this made many cool Mercs worthless.

Mercedes-Benz is a brand known for the production of reliable luxury cars. However, you might reconsider buying a Mercedes-Benz manufactured between 1991 and 1996.

In the 90s, to comply with the government's environmental mandates, Mercedes-Benz parts supplier Delphi supplied the Stuttgart automaker with biodegradable wiring harnesses for insulating electrical lines. As the name suggests, biodegradable wiring harnesses degrade over time. Although the idea was spectacular and environmental-conscious, they failed to conduct adequate tests with heat.

Would you knowingly buy a Mercedes-Benz with exposed electrical lines? Probably not. Exposed electrical lines increase the risks of short circuits and corrosion of the wires. For that reason, 90s Mercedes-Benz cars are worthless today as most sell for fifteen times lower than the prices when new.

Related: These Mercedes-AMGs Will Bankrupt You Through Repairs And Maintenance

Mercedes-Benz mainly used biodegradable wiring harnesses for top engine wiring. The engine wiring harness controls a vehicle's electrical system by controlling information and relaying power to other components.

A car owner's last desire is to have exposed wires connecting the control units and various car sensors and actuators. Prolonged exposure to heat affected the biodegradable wiring harnesses, making them break.

The most affected wire lines were those to the ignition system and the throttle valves since the biodegradable materials cracked and fell off. Moreover, the engine's ceaseless vibration made the insulation flake and crack, exposing the copper wires.

The Soya-based biodegradable wiring harnesses are poor heat resistors. The consistent heat from the engines hardens the material making it crack and fall off over time. The exposed copper wires will likely lead to electrical short circuits when they come into contact with the vehicle's body or other electrical lines.

As indicated earlier, throttle valve actuators were some of the most affected components because of Mercedes' biodegradable wiring harnesses. Exposure to dust and other corrosive materials leads to exposed and corroded copper wires. Corrosion increased the copper wire resistance. When the electrical lines connecting the electronic fuel injector control unit and the fuel injector corrode, it leads to misfiring.

The defects in the engine's wiring harnesses may affect the lighting system due to defects in the electrical lines that may disrupt the supply of electrical energy. It is mainly noticed when the car's lighting is dim.

The spark plugs and the engine's starter motor requires considerable electrical energy to generate a spark during ignition. Faulty wire harnesses may fail to transfer the electrical energy resulting in engine failure to start.

The defects in the wiring harness may affect the electrical lines between the battery and the alternator, resulting in a lack of or poor battery charging leading to a dead car battery.

If any of the mentioned issues occur in your 90s Mercedes, it is paramount to check the wiring harnesses to make the necessary replacements.

Related: The Spectacular Failure Of The Chrysler PowerTech 3.7-Liter V6 Engine

The production years of the Mercedes Benzes are insufficient to determine the models and engines affected by the biodegradable engine harnesses. The most effective way is to identify the fuel injection system utilized in the 90s Mercs.

The auto manufacturer used the biodegradable wiring harnesses on the Mercs with the LH Jetronic fuel injection systems. The issue was common in the straight-six M104 engines from 1993 to 1996 and the V8 M119 engines from 1991 to 1996. Additionally, the biodegradable engine wiring harnesses affected all the other Mercedes engines that utilized the LH Jetronic fuel injection systems between 1991 and 1996.

Although Mercedes-Benz from the 90s had biodegradable wiring harnesses, they also had exemplary interiors and reliable engines. For Mercedes-Benz enthusiasts, staying away from such vehicles might be tough.

Hence, when buying a Mercedes-Benz from the 90s, the buyer should be ready to replace the entire engine wiring harness system. Lack of fixing the biodegradable wiring harnesses may lead to some serious safety issues.

Before purchasing the vehicle, a buyer should ensure it is in immaculate condition. Replacing the entire engine's electrical wiring harnesses is relatively affordable. However, some buyers may prefer buying a newer Mercedes-Benz rather than buying one from the 90s and replacing the wiring harnesses. The biodegradable engine wiring harnesses have resulted in the loss of the 90s Mercedes value in the used car space, making them worthless today despite Mercedes selling them for premium prices at the time.

Take, for example, the 1994 Mercedes-Benz SL-Class. The base SL 320 sold for an MSRP of $85,200. But today, a used 1994 SL 320 goes for an average of just $13,000! That's a huge drop in value, despite this Mercedes coupe being a desirable driver's car.

Sources: Donut Media Via YouTube,

John Waruingi is a car enthusiast who enjoys attending meet and greets and car enthusiasts meetings. He has interacted with cars from the age of 10 when he would visit local garages to learn more about cars on weekends. He enjoys driving rebuilt classic vehicles, helping in after-market mods, and doing drag racing. He aspires to take part in car rallies in the future. Currently, John represents HotCars and writes automobile-related articles to share his knowledge with the world.