They’re Putting Soy In Your Wires, Man

I’ve got a friend who tells me at every opportunity that soy is the downfall of humanity. Whatever ails us as a society, it’s the soy beans that did it. They increase violent tendencies, they make us fat and lazy, they run farmers out of business, and so on. He laments at how hard it is to find food that doesn’t include soy in some capacity, and for a while was resigned to eating nothing but chicken hot dogs and bags of frozen peas; anything else had unacceptable levels of the “Devil’s Bean”. Overall he’s a really great guy, kind of person who could fix anything with a roll of duct tape and a trip to the scrap pile, but you might think twice if he invites you over for dinner.

A column of soy soldiers stand at the ready.

So when he recently told me about all the trouble people are having with soy-based electrical wiring, I thought it was just the latest conspiracy theory to join his usual stories. I told him it didn’t make any sense, there’s no way somebody managed to develop a reliable soy-derived conductor. “No, no,” he says, “not the conductor. They are making the insulation out of soy, and animals are chewing through it.”

Now that’s a bit different. I was already well aware of the growing popularity of bioplastics: the PLA used in desktop 3D printers is one such example, generally derived from corn. It certainly wasn’t unreasonable to think somebody had tried to make “green” electrical wiring by using a bioplastic insulation. While I wasn’t about to sit down to a hot bag of peas for dinner, I had to admit that maybe in this case his claims deserved a look.

Frustrated Motorists, Happy Rats

Sure enough, a Google search for “soy wires” will get you plenty of hits about people who are experiencing a very strange problem. During the night, animals are getting up into the engine compartments of their cars and eating the insulation off the wiring harness. It isn’t just one or two cases either, it’s enough of a problem that some car manufacturers are getting hit with class-action lawsuits.

Daniel Dobbs, et al. v. American Honda Motor Co. Inc claimed that Honda vehicles manufactured from 2012 to 2015 made use of soy insulated wires on the basis of it not only being better for the environment, but cheaper than traditional insulation. Unfortunately, this type of insulation is also very popular with the local wildlife:

Unbeknownst to Plaintiffs, however, a real and contentious unintended and undesired consequence of this soy-based insulation material is that it attracts rodents and other animals that are drawn by the soy content of the insulation, and proceed to chew through the insulation and electrical wires that the insulation coats

A few months later, a similar lawsuit was filed against Toyota for the same soy wiring used in vehicles between 2012 and 2016. Yet another lawsuit targeted Kia. Forbes even published an interview in early 2017 about a woman who’s 2016 Volvo was constantly being attacked by critters, to the point that she had to order coyote urine off the Internet and sprinkle it around her car every night as if she was performing some magic ritual.

There’s even a website called, get ready for it, howtopreventratsfromeatingcarwires.com that collects information on this peculiar situation. The owner of the site details the trouble they had with their own 2015 Honda Civic, and lists makes and models of vehicles which are known to use soy wiring. There’s even a fairly regularly updated blog with articles ranging from the rationale behind using bioplastics to identifying rat droppings in your engine compartment.

Nearly $2,500 in damage caused by rats eating soy-insulated wiring.

Lawsuits Dismissed but Questions Remain

Looking into some of these class-action lawsuits, we can see that they are often quietly dismissed. This is of course quite common in cases like this: the manufacturer writes a fat enough check and the plaintiffs willfully dismiss the case, generally with the understanding they won’t mention the situation again. Who can blame them? If Honda or Toyota handed me a check with 4 or 5 zeros, I can’t say I’d push the issue either.

But why aren’t reports more common? Given the range of manufacturers and model years listed in the class-action lawsuits, it seems this issue should be more widespread. Is there another variable at work? The Forbes article claims a representative from a Volvo dealership in Michigan let slip that the issue only seems to crop up in more rural areas, never in cities. Perhaps food scarcity has to hit a certain level before rats will get a taste for soy-based insulation? While we’re on the subject, are soy-based bioplastics the only ones susceptible to this problem? Do we need to add rats and mice to the list of things we must protect our rolls of PLA from?

We’re curious to hear what the good readers of Hackaday think about this rather unique problem. Do potential issues with bioplastics give you concerns about using them in your personal projects or commercial products? What about the poor souls who are stuck putting rat traps under their tires every night? Is there some solution the Hackaday community can come up with to counteract this particular quirk of bioplastic insulated wires?

108 thoughts on “They’re Putting Soy In Your Wires, Man

  1. Might not smell too good, but something like (modern) mothballs might help keep them away. I dunno if you wanna put the old fashioned naptha ones in your engine bay or not where they might combust.

    1. True, but at what point does this cancel out the “green-ness” of the product? And if you use some kind of repellant it might wear off in a few years, plus it wouldn’t protect against becoming brittle or biodegrading in nastier climates. So you’d need some kind of preservative. Seems like it misses the point.

      Insulators are one of the really legit uses for immortal plastics. Biodegradable plastics would be great for the uncountable little wrappers and bits of packaging in the world, but making electrical insulators out of it is a big stupid greenwashing campaign gone wrong.

      1. +1
        Who wants/needs/“thinks it’s a good idea to have” degradable electrical insulation? That is just a ticking time bomb that will force obsolescence of the new cars and make people buy new cars as their old cars deteriorate or get eaten by rodents…
        On second thought maybe there are two different motivations at work here.

      2. Volvo used some really lousy wiring insulation for a few years in the 80’s. Some people call it air-soluble insulation. It just falls apart after a while, along with several other plastic parts in the cars.

        1. Mercedes had a similar problem in the early – mid 90’s. “Biodegradable” wiring harnesses because of environmental standards. I’m not sure what’s environmental about replacing your wiring harness…

        2. I’d argue that carried on into the early 2000s. I’d keep getting strange CAN bus errors on my S80 T6 that were not based in fact. I would say my Volvo was an early source of “fake news”.
          I had connectors fall apart in my hands so they were probably made of the same air soluble material.

      3. I totally agree that in this case something has gone wrong, however i feel the need to set something straight that is also misleading in the article: I think this is about biobased polymers (the better term according to IUPAC; https://en.wikipedia.org/wiki/Bioplastic) which are probably “greener” if you only look at manufacturing compared to petrol based stuff. However it nowhere says that this story is about biodegradable polymers (not all biobased polymers are biodegradable).

    1. Last week my parents had to spent 120€ on their 6 month Volkswagen Golf after visiting us for the birthday of our son. Interestingly the mechanic told them it’s a known problem. It didn’t bother him to take the money…

        1. True story: my wife (German) was trying to explain to me why people put chicken-wire grates under their cars. She had thought the martens were into timing belts (which they may be for all I know).

          Anyway, somehow this turned into Martians trying to eat through time.

          You can also buy cayenne pepper spray, and little random beeper devices that supposedly scare the martens away.

          But Marderschaden waaaay predates using soy in wire insulation. I guess they just like the way it feels in their teeth or something. (Tell me you’ve _never_ chewed on insulation after stripping a wire.)

          1. Of course these “beasts” always liked cable and I wouldn’t wonder about the defect.

            What surprised me was that the VW-mechanic admitted that it is a known problem of the current model which uses plastics including meat-and-bone meal for the wiring.

            Regarding the chewing: I can’t remember, but if I could I wouldn’t admit it 😊

  2. Reminds me of the biodegradable wiring that some European cars used in the ’90s, except that often gave about 10 years of service before falling apart. On those cars, there’s not much to do other than get wiring with better insulation, and that may be the only fix for soy wiring too.

    1. … Incurring even more environmental waste as would happen normally. This is just a cynical PR move, not a serious attempt at helping the environment. And it’s probably gonna catch someone’s car on fire.

    2. My 1992 Mercedes 500se had soy wiring. I do believe the manufacturer was trying to be green and not cut corners. However the heat and movement would destroy it. I completely rebuilt the upper engine wiring harness but other cooler wires were fine. Apparently Mercedes changed back to normal plastic once this issue was identified. So don’t buy an early model. There was not a uk recall.

      1. I recall reading a decade or so ago, to not buy a certain era Mercedes because of “faulty wiring”.
        I had no idea what they meant. I was wondering If Lucas was building their wire harnesses.

  3. soy makes a great environmentally friendly plastic.

    just like corn did in the 70s and 80s.

    i would rather release phosgene gas when burning the wire to strip it for scrap or using the hot wire stripper tool than to have wires chewed and burn down the car or house and even kill a couple sleeping (csi the theory of everything)

    1. Burning insulated wire? Bad practice – you’re not only damaging the environment (and probably your own lungs) but also degrading the copper. Many scrapyards won’t take it if they notice.

      1. Scrapyards usually don´t buy burned/charred copper because of the chance of it being from stolen wires, not exactly because it is burnt. Also, sometimes people will mix non-copper wires and burn them along with the real copper ones, to increase weight.

  4. That could explain why our ginny pigs keep eating the wires insulators of our equipments (computer and Phone chargers, all kind of New power cables). This issue doesn’t happen with old cable.

  5. This won’t be remedied without pervasive lawsuits because guess what — animal damage is excluded from the warranty, so it doesn’t cost the carmakers anything.

    This will be the kind of problem that gets stalled/settled/spun until nearly all the cars are off the road from age and then there’ll be a recall (looking at you, Volkswagen wiring division)

  6. My google-shui is failing me, but hasn’t the telecom industry (somewhat) solved this problem with bad tasting layers in outdoor wiring? If true, would the foul-flavoured additive defeat any environmental gains the soy products provide?

    1. One of the toys my daughter got for Christmas this year had a little slip of paper in the box explaining it had been treated with a “bitterant” to dissuade children from putting it in their mouths (at least, more than once). So if it works on toddlers, I suppose might as well try it on other wild animals.

        1. It takes an insanely small amount of Bitrex for something to taste (really) bitter…and since you’re not supposed to dump antifreeze into the drain anyway, the small amount of Bitrex should a lot more good instead of bad.

    2. I read some years ago in a telco magazine about a phone company that had problems with squirrels chewing their overhead lines. So they had a company come up with a way to mix capcaisin oil into the insulation plastic. The squirrels developed a taste for hot pepper insulation.

    1. My point exactly. I once had to deport a rabbit who chewed through every wire he could find. Speaker cables, computer cables, extension cords etc etc etc. Rabbits may look all cuddly and fluffy but they’re EVIL !

      1. Satellite cable used to be a ribbon of 4 cables. 2 for signals (C/Ku), one for dish pointing and one to run the polarity servo. About a dollar a foot wholesale. I had a run that went from my apartment, out my balcony and up to the roof. Somebunny’s bunny got loose and snacked on the balcony part of it. Splicing was not an option. Over $100.oo to replace!
        Cockroaches used to (and may still) eat the insulation in TVs and stuff too.

    2. There are so many points of contention with this soy wiring insulation story. Are the rats actually consuming it or are they using it for bedding? I doubt they could use it for food after it has been polymerized. The whole thing almost sounds like a shade tree mechanic theory run wild.

          1. They may have been attracted by the French Fry aroma of the bio-fuel, and decided to have a side of insulation. Can you imagine what hot soy and bio-fuel must smell like to a rat?

  7. Anyone have chemical details on using plastic insulation derived from soy? It’s a bit naive to think the end product necessarily has any trace of the soybean source, and really kind of misleading to the public if it has nothing to do with the environmentally friendly nature of the polymer.

    For example, my immediate guess is that they switched from some PVC-base to a polyurethane-base polymer. PUs are nice polymers, and they’re sort of easy to make ~50% bio-derived – the polymer is typically made through a reaction between an isocyanate and a polyol. Polyols are organics with lots of alcohol groups – and yep, they’re also known “sugar alcohols,” and many edible sugars (including sucrose!) have been used to make PUs.

    My suspicion is that the edibility of the wires was influenced more by the change from PVC to PU, rather than the soy base. If the polymer was formulated correctly, that original purified polyol feedstock should have been fully reacted and I doubt there’s much that was still digestible in them.

    In New York, rodents have eaten up plastic wiring in walls, well before any “environmentally friendly” plastics came to be. In fact, the local electrical code requires all electrical wiring to be sheathed in steel conduit. Admittedly, this might be because the local breed of rats is particularly aggressive, but I think this just illustrates that it’s not unreasonable that animals might just randomly munch on any plastic wiring for random reasons. Maybe it’s a normal occurence, and now everyone who’s been trying to figure out why animals have been hiding in their car is attributing it to soy-based wiring.

    1. Hell, when I was a toddler, even I chew the insulation on wires, and also shiny polished furniture (nitrocellulose, or acetate, I presume), I remember it crackled so nicely under my teeth – so, I understand why rodents would do it.
      I hope I didn’t damage my brain :( …

    2. Properly cured PU material actually has no real appreciable odor, unlike PVC which constantly gives off both odors and flavors as well as phthalates, which PU doesn’t need to have to make it flexible nor does it contain. Animals have been consuming or chewing on PVC based wires for many years.

      Plasticized PVC insulation has historically been cheaper than PU material though PU material is mechanically and chemically and safety and longevity and environmentally wise a much better material.

      Things are starting to change though quite slowly and most consumers can’t tell the difference until things like their entire cord grows mold or animals eat their cords happen because the cord’s insulation was made from PVC.

      Gotta save a few bucks on the ENTIRE WIRING HARNESS FOR THE CAR, simply to save a very, very small amount per vehicle after all!

      That or go fiberoptic, which many manufacturers are starting to incorporate.

      1. Squirrels will happily munch on fiber. The CLEC here had a sudden outage. They traced it to a fiber junction on a pole at the end of the alley behind their office and server building.

        When the tech removed the cover a squirrel jumped out and ran. It had somehow squeezed itself down the cover channel on the pole, despite it being mostly full of cable, then when it got to the box at the bottom it tore up a large number of fibers.

        So they had to pull things out, cut the fiber bundles back then splice in a new section. I assume they also figure out a better way to seal the top end of the cover channel to keep out more exploring tree rats.

  8. Somwhere late in the 80’s Elektor had a pcb for a ferret repellant. Supposedly in germay ferrets ate insulation under the hood. Back then this was due to fish oil being used in the insulation

  9. Mix some million scoville capsaicin extract into the plastic before molding it. It works to keep squirrels off pumpkins at halloween, I have to think it would make the insulation less delicious.

  10. as an auto-spark I con confirm this is a thing, and its been going on a long time never knew it was soy tho, always figured it was something in the cloth wrapping that protects teh wiring from abrasion.

  11. On vacation, we parked our Subaru outside and left it unused for a few days. Some rodents got to the wiring. The dealer told use that the Boxer engine is the perfect size and shape to make a nest for rodents! So, some models had problems with animals, and some did not. Presumably they all had similar wiring harnesses, but different sized engines. I don’t buy it that soy is the problem.

  12. I have had similar issue, however the explanation was that the rodents and especially martens, are attracted to the fish-oil based release lubricant used during the production of the rubber hoses in cars, this is especially an issue with new cars, once they are half a year old the problem seems to go away. Standard car insurance (in Switzerland) covers damage due to martens chewing on cables and hoses.

    1. Bzzztt.

      It wouldn’t be hard to diagnose the fault but would you have a fault clearance code for it lol.

      In the past I have asked for codes for things like –

      replaced quasi-nuclear-phase-locked-loop-synthesized-equalizer

      reset customer expectations

      adjusted customer psychology

  13. During WW2, Illinois (and perhaps other states) issued plates made of compressed soy to save on metal going to the defense factories. Goats had a field day going around eating them.

  14. In my experience many rodents like mice will happily eat through things definitely not made of organic materials.
    So consider that before trying to solve something the wrong way.

  15. “Yeah, that’s what I thought. Mynocks. Chewie, check the rest of the ship, make sure there aren’t any more attached. They’re chewing on the power cables.”

    Who knew it was the soy they were after?

  16. Here in Australia I haven’t encountered anyone mentioning a situation about rodents eating insulation, but then again I live in a major city and not in the country. My biggest problem are GECKOS. These sure-footed litle b**tards walk all over everything, leaving their little calling cards, which can be on vertical or sometimes even upside down surfaces. They get into small spaces such as through the vents in compressor motors and computer cases, and also the house roof ventilation slots. Having a tarpaulin over a vintage car means nothing to them, they just go inside. Absolute pests, they are.

  17. I have no doubt that rats and other animals are fond of chewing wire insulation containing soy products. They may do it for the taste though I think it’s mostly for the joy of chewing (you should see my dog go to town on the plastic chew toys we give him – probably made of the same stuff). I do have an issue with the first few sentences of this post, however. While I acknowledge that Mr. Nardi was referring to a friend’s hopefully tongue-in-cheek opinion, I think that the notion that “….soy is the downfall of humanity. Whatever ails us as a society, it’s the soy beans that did it. They increase violent tendencies, they make us fat and lazy, they run farmers out of business, and so on.” is a bit of a stretch. Just so you know, half the world eats soy products daily in all three meals and have been doing so for centuries with no violent tendencies whatsoever. I’ve lived most of my life in Asia and I can tell you that the people here are some of the most peaceful, fit and productive people I have ever known. Then again, there is always the exception, whom I need not mention by name. Makes you wonder what kind of insulation they’ve been eating…

    1. I think the author was trying to set a mood by suggesting his friend was a bit crazy. Thus making the whole idea, and story, more entertaining. If anything Soy would feminize people a bit because of the phytoestrogen. Because we all know how placid women are. (I already slapped myself for that last bit, so no flames please)

  18. long chain of reactions, so I do not know if it was already mentioned, but this is text from a patent from a google search on using fish oil in wires:
    “I have found that if ordinary rubber is dissolved in a heat treated oil, such as a vegetable or fish oil, a new and improved rubber varnish or enamel is obtained. Preferably this is accomplished with the use of a vegetable oil which has already been heat reacted to its resinous point so that it is in the form of a fiuid oil resin. Among the oils suitable for this purpose are, soya bean oil, cashew oil, China-wood oil, etc. I may also use an animal oil such as menhaden, 3 sardine or one of the other fish oils. ”

    So in order to improve the quality of the insulation they dissolve rubber in vegetable or fish oil, and use the result like a varnish. Guess that leaves a bit of the taste of it in there, especially if gets too hot (go google fishy smell in house for instance).

    1. Many moons ago, I think it was the early 90s, I experienced a strong fishy odor that I eventually tracked to an 8mm video cam from (Insert all brand names here). Several companies were making the same model with slightly different features. The thing is, to fit all the necessary components into such a small package, they had over rated the electrolytic capacitor voltages. (Lower voltage caps are smaller). I discovered that there were “Cap Kits” available from several parts sources, and so concluded that this was a “Known Problem”. It turned out that the smell was a highly carcinogenic by-product of the PCB based oil electrolytes they used (Also to allow them to make the caps smaller). The smell got much worse when the units were warm. If you have one of these things, put on your rubber gloves, place it in a thick plastic bag, and call HasMat. Or check to see if rats like them enough to eat one.

  19. Now wait a minute! Soybeans has been grown and consumed in Japanese cuisine for centuries, and the authors are telling us that all of the sudden “young people in Japan stopped having sex”?

  20. “16 Signs Japan Is Obsessed With Soybeans”
    “Why have young people in Japan stopped having sex?”
    “What happens to a country when its young people stop having sex? Japan is finding out…”

    These all sound like papers from respectable journals.

  21. Toilet bowl cleaning block zip-ty’ed to the cables in the engine compartment seems to de the trick so far. The Toyota garage was a bit confused by this solution but no other side effects. Replace every few months.

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