Biodegradable wire insulation

I have a 2000 Mercedes CLK, and it recently started having electrical problems. Next, I discovered that back in the early 1990s, The EU started requiring cars to have biodegradable wire insulation. The first few years (1992-1996) are supposed to be the worst. On my car, I noticed some insulation cracking on the headlght wire harness. Then I found that the trunk wiring harness has the same problem.

I am wondering: do all European cars still use biodegradable wiring insulation that falls apart? How long is it expected to last? Do Japanese and American cars have the same problem?

You’ve got an 18 year old car . . . I would expect it to be in worse shape, versus when it was new

You can get headlight socket pigtails for cheap at Pep Boys or other major parts stores. Just splice a new one in, as needed

As for the “trunk wiring harness” . . . exactly what isn’t working? There are some wires running along the trunk lid hinges, for the chmsl and the rear fog lights, which are located on the trunk lid, underneath the paneling. The wiring often breaks down, after years of flexing. You can easily fix it, once you’ve determined where the break(s) are.

But none of these problems are specific to european cars. I’ve seen those exact same problems on Japanese and domestic vehicles, for example.

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No. My 2001 Saab’s wiring is fine.
My 2004 Chevy’s wiring is fine.

All wire insulation will eventually break down. How long depends on the material used on your particular car and the environment it is subjected to. Hot dry places tend to destroy wires over the course of 15 years or so.

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That is what I thought about my Mercedes until recently. But if you look closely at the wires on your Saab, is the insulation brittle? Does it crack if you bend it?

I yelled at Mercedes about the problem, and told them that they used the wrong insulation. Their response is that I was lucky to go 18 years without a problem.

I’m sure that helped.

Your car is 18+ years old, there is a cost associated with keeping an aging car on the road, and repairing wiring is one of them.

I’ve replaced headlamp wiring pigtails on many makes of cars. It’s not unusual.


No and No. I do ALL the service work on this car. I am very familiar with it.

Yup, I agree with MB, you were lucky.

If you do an internet search on biogdegradable car wiring, you’ll see what I am talking about. I am not crazy.

Nobody said you were crazy

I happened to be a mechanic at a Benz dealer for many years, and I’ve seen a few deteriorating harnesses

Rational people do irrational things, and yelling at the dealer and/or corporate is irrational. It won’t get you anywhere. It’s not as if the engine and/or transmission have failed. Your problems are relatively minor. Fix the wiring and move on

My mom’s 1999 Benz doesn’t have any problems with the wiring, as an example. so just because it happened to some, doesn’t mean it will happen to all

Bottom line . . . you’ve got an old car. the dealer and manufacturer owe you nothing


The Mercedes customer service rep tried to tell me that all wire insulation disintegrates after 15 years. That is simply false. If you spec the right wiring insulation, it doesn’t fall apart after 15 years. But the question about how to treat customer service reps that don’t know what they are talking about is off topic. From what I can tell, cracking wire biodegradable wire insulation is a very common problem. I’d like to know: does the EU still require biodegradable wiring insulation in cars? Is it required in the US and Japan?

The insulation on the wires of my '87 Toyota pickup is okay.

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My 25 year old Corolla was manufactured in the USA. The wiring insulation in both the engine compartment and trunk remain in excellent shape, the trunk wire harness I was looking at just the other day, and appear new. I’ve never heard of a bio-degradable wire insulation rule in the USA.

The wire insulation in my 45 year old Ford truck remains functional, but is showing some signs of degradation in the engine compartment and tail-light area where it is exposed to the sunlight & weather.

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I don’t believe it is required in US but since car manufacturers market worldwide and prefer economies of scale, as long as it is required in one, all will be affected. The material composition has been changed since those early years but the fact remains, if it is biodegradable it will break down sooner than a petroleum based product like PVC. The other issue is that it is now edible and rodent damage is on the upswing. Here’s a pretty decent write up on an unusual site for the topic. Google plenty of info if don’t like this one -

The wiring in my son in laws 1950 Chrysler is all original and in fine shape.

I had an '85 SAAB 900 which suffered the deteriorating insulation problem. Badly. I’ve also seen a few other SAABs with the same issue and which caused all kinds of grief.

One could split the loom open with a razor blade and all of the wiring insulation had turned white. Rolling it between the fingers would cause it to crumble into dust.

without reading the article, I don’t know about biodegradable insulation but around here they started using soy based insulation which might be the same thing. The rodents love it. Save the planet.

Poor logic by the legislators. Biodegradable insulation causes the cars to be junked earlier, which is much worse for the environment than some wire that degrades slower.

Biodegradable wire insulation is just plain dumb IMHO.

Someone should write a book about all the dumb things that auto manufacturers have done to try to comply with virtually unattainable (without serious compromises) government mandates. Biodegradable electrical insulation is right up there. I suspect that automatic stop-start systems will be at the top of the list too. Along with engines that run on only some of their cylinders when the system determines that all of them aren’t needed.

Next thing you know they’ll have biodegradable tires. Whoops! Don’t pass that idea on! As much as I hate tire piles, having my tires disintegrate under my nose is a very dangerous solution! :stuck_out_tongue_winking_eye:

Wouldn’t want your tires to suddenly “disappear” at 75mph in the left lane on a freeway, with lots of cars following you

Also wouldn’t want them to disappear when passing a semi pulling 2 or 3 trailers on a one lane road

Nope. And I wouldn’t want the tires on the semi to be biodegradable either! :open_mouth:

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