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Comment by kube-system | Hacker News Reader

> Turns out that actual cars don’t have individual cables. Instead they have these big “looms”, which bundle many cables from a nearby area into a single harness. This is the reason why I could not find the individual cable earlier. They simply don’t manufacture it.

I was really surprised to read this at the end of the article -- how could someone be this deep into a project of this depth and not realize this?! Not only because all cars (...er... all vehicles) are wired this way, but also because the documentation they were referencing has plenty of detail to show this... there's even a whole picture of it (and to Tesla's credit they have amazing free docs): https://service.tesla.com/docs/Model3/ServiceManual/2024/en-...

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> and to Tesla's credit they have amazing free docs

Not to Tesla's credit, they had to be dragged kicking and screaming into it (primarily by Massachusetts) and their right to repair legislation through a solid chunk of malicious compliance:

1. When told that they had to have a site for people to order parts, Tesla put up a site that had every single item as "Call us", including the most simple of bolts. And when a few places called, "Sorry, that's not available to you".

2. The service manual was originally only available in a few locations in MA, and had strict conditions: you had to book in advance, there was a $100 fee per booking, and you could only view the manual on premises, and could not bring electronic devices into the room with you, just pen and paper.

The docs they have are great, and who knows how their attitude would have changed over time, but they absolutely didn't want you to have it, initially.

Tesla treated the service manual like congress treats certain recently surfaced files.

Wrong. They’ve always been open, even with their patents too. All free to use, no royalties

Confidently incorrect.

https://www.reddit.com/r/teslamotors/comments/utivlj/tesla_s...

> This used to cost $3187.50

https://driveteslacanada.ca/news/tesla-service-manuals-free-...

> The access story has been inconsistent over the years. Tesla has opened up free access to both the service manuals and diagnostic software in the past, but that was apparently a mistake, and loopholes were quickly closed.

https://www.teslaownersonline.com/threads/tesla-service-manu...

"Always ... all free to use". Not so much. And before that, even less available.

I will grant you for number 2, there seems to be some ambiguity - some people claimed it was only if you needed to actually use their diagnostic tools, because Tesla wouldn't sell them to anyone at the time (which is also in contradiction to your "everything you need, all free, always").

Diagnostic tools are built into every car and free, service mode is amazing. No other car manufacturer does that.

Elementary diagnostic tools are free.

If you think this is actual diagnostic tools? No.

Free? Weird that Tesla offers a subscription for it: https://service.tesla.com/en-US/diagnostic-software

$700/year is a strange definition of "free".

You seem to miss my point. The OP wanted to pat Tesla on the back for their amazing commitment to freeness and openness. My point was that even if they are doing good/much better now, much of the time they had to be dragged kicking and screaming to it. MA's AG had to wave the right-to-repair laws.

It's not uncommon knowledge that third party repairs have been, for years, difficult to impossible because Tesla wouldn't supply either the information or the parts to third parties. I'm not sure why, in the face of repeated evidence otherwise, you seem determined to retcon those details out of existence.

No, you’re wrong. I have a Tesla and service mode is free and amazing, I can look at any system and subsystems with it, look at logs, and do testing, all from the built in touch screen all for free. No other car manufacturer comes close. Not sure why you hate Tesla so much and are so bent on spreading false information. Maybe you should help save the planet and get one.

Maybe you should read Tesla's own documentation. The service mode you have is an elementary version of diagnostics. There is an actual diagnostics mode that costs $700/year to have access to.

Again, since you plainly didn't read it: https://service.tesla.com/en-US/diagnostic-software

service.tesla.com - if I'm spreading false information, so is Tesla. Oops.

Is plenty enough to do full diagnosis on the car. Far better than any other manufacturer does. Give me one that’s better.

Makes you wonder why they sell that, then, huh. Obviously nothing fruitful is coming from further interaction here.

Well the AG has a lot of work to do then, because basically all other manufacturers are charging thousands for any sort of diagnostic manuals

GM service manuals for instance are $1,344.00/year.

Ford service manuals are $2,834.95/year.

Honda service manuals are $1,500/year.

Hyundai charges $600/year.

Toyota service manuals are a steal, they only charge $580/year.

> how could someone be this deep into a project of this depth and not realize this

I think this is a software guy who occasionally dips into hardware things (to hunt bugs).

That's what I figure -- but it was wild to read that after reading the part about component-level PCB repair lol

Yeh, it seems odd to have the cut off cables, the wiring information...and then to go and buy a loom rather than bodging a cable at that point.

> I was really surprised to read this at the end of the article -- how could someone be this deep into a project of this depth and not realize this?!

Usually, for most other vehicles, the connectors are either standardized (e.g. radios, ISO 10487 [1], high-current chargers by VG 96917) or the foundation plugs, sockets and re-pinning tools are readily available by the vehicle manufacturer or by aftermarket suppliers.

Tesla truly went out of their way to make the life of third parties (such as wire harness repair shops) more miserable here.

[1] https://de.wikipedia.org/wiki/ISO_10487

Even if you know that cars consist of a single wiring harness, it's not implied that they aren't modular and the individual cables cannot be purchased separately.

Cars usually consist of multiple harnesses -- as it is in this case as well. The harnesses are the cables in a car. That is the part you can purchase because that is the part.

There's a list of them here: https://service.tesla.com/docs/Model3/ServiceManual/2024/en-...

I was more fascinated that a new wiring harness was $80! I've easily spent $30-50 for a single VAG cable 1ft pigtail.

EVS have actually managed to reduce the number of wire bundles (mostly due to switching to Ethernet instead of CAN Bus)

Tesla also went to a 48v wiring harness in some of their vehicles to allow them to power more equipment with less copper. It might be one reason why they use nonstandard connectors, so people don't attempt to hook 12v equipment to the system and also the higher voltages might require connectors rated for it.

Now they just have to take the next step and have everything in the vehicle running on PoE.

How?

When canbus is already two wires, and by definition, is a bus, so you can just keep stringing those two wires to any module you need. I know Ethernet BUSes exist, but what advantage would those have to canbus then? They're both two-wire buses.

Canbus is much slower than single-pair Ethernet. So you can get more data (more modules connected) over a single pair of wires if you switch to Ethernet.

I will say I’m surprised how far apart the two boxes are in the car. I guess they’re not where I thought. I would assume they’re both up near the dash.

The passenger side kick panel or behind the glove box are two very common places for vehicle computers -- some cars have them under the hood, which I always thought was a bad idea.

My RAM truck with the Cummins diesel engine has the engine computer mounted on the engine block. You'd think the heat and exposure to the elements would make that a bad idea, but I suppose Cummins knows what they're doing.

Hehe I was thinking about FCA/Stellantis vehicles when I wrote that. I know it works and there are components made to work in that environment but it always felt intuitively wrong to me. Especially when the other side of the firewall is a much better environment and not far away

It’s because when placed inside the engine bay, the large wiring harness is shorter, which is not only cheaper, but also shorter wiring helps with the consistency of electrical timing and reduces noise.

Yes they do. They can tolerate engine bay heat, but not exhaust heat. They are usually shielded from getting soaked.

Some Mazdas put the metal-cased engine computer in a plastic air box that feeds cold air from the front, to help ensure the engine computer stays cool enough.

In general, I believe the cooling airflow from the frontal air and the cooling fans keeps engine bay in check.

For example, this is the board that’s used in Mazda CX-5 2017+ engine computers (mfr Denso), it lists max temperature range of +150C: https://www.renesas.com/en/document/mah/rh850e1l-users-manua...

Yeah, on the Cummins the ECU is mounted on the intake side of the engine away from the exhaust and turbo and toward the front right under the fuel injection pump so it gets lots of cooling air.

This thread is interesting to me 'cause I'm also a software guy and recently took a job dealing with building fighter jets and the amount of engineering going into the wiring and computers on those things is insane. It's been a very interesting learning experience.

My car has it under the passenger seat.

Sounds alright until you realize after spilling a bunch of flower vases in the trunk (hatchback) that the computer has literally no case on it and immediately shorts out while driving. Or a passenger spills a drink in the rear seat cup holder.

There is now a recall notice to pull the back seat out to install a $5 plastic cover over the thing.

And yep, it’s the main computer for the car which controls the electronic transmission etc. Immediate full on engine-shuts-off at speed on the freeway and you require a flatbed to tow it away level of broken. I’m sure the engine ECU is in the engine bay, but holy hell what a surprise!

I had a car with an all wheel drive computer in a similar spot in the late 2000s.

I had a small crack in the rubber seal around my sunroof from parking outside in the elements. When it rained, water seeped in, made its way down the a-pillar, pooled under the seat, and fried the computer.

Expensive fix but I was able to drive it to the shop.

Could be because they sale crate engines.

If you'd like the cursed location for a vehicle computer, have the Smart fortwo's SAM. It's the fuse box!

It's also notorious for having awful solder connections and failing outright.

https://evilution.co.uk/mod/sam-unit-solder-repair.htm (and Aging Wheels: https://www.youtube.com/watch?v=n8AAleKR33Q)

I'm sure you're an expert, pro at everything.

Yes I am. Thankyou for recognising that

I wasn’t criticizing them.

Software people tend to overestimate their knowledge of other disciplines, writing it off as "easy" or work beneath them. Being overpaid compared to your peers certainly doesn't help dispel this feeling. Some people have built entire careers around designing wire looms.

There's a reason that John Salvatier's 'Reality Has A Surprising Amount of Detail' blog entry is so evergreen on this forum.

> Software people tend to overestimate their knowledge of other disciplines, writing it off as "easy" or work beneath them

You should see what happens when someone involved in the sciences, e.g. Chemistry, gets their hands on Claude Code.

What happens?

A professional scientist I know (tenured, professor) recruited me to set up a backtesting framework for a predictive finance model. When the results were not as they expected (this person does not work in finance and never has), they asked to see the code, then told me that claude had found a problem with the way some of the calculations were done (there was actually no problem), supplied the claude comments, and told me to change the code to match what they thought was correct. I did it anyway. Had they had more expertise in the domain (finance), they likely would have been able to leverage claude as a tool rather than inadvertently pursuing a very stupid mistake. Domain experts tend to doubt their ability to excel in other domains which is amplified by LLMs.

I work with a bunch of PHD's and have been since before ai coding.

Their code is aways terrible, and they constantly think it's good.

The exercise is always the same: explain the math to me, like I'm 5, then we profile it and see what is faster.

Oddly Claude Code, integrated into their IDE's has made this situation happen much less.

I never want to work in a place again where the fun way to start the Monday meeting is a "math problem".

PS: Don't even get me started on their SQL.

My first job out of university was at IBM wrangling a prototype some research PHDs had written into a shipping product, and.. yeah, this tracks.

This sounds rather similar to the form of scientific fraud where you first create a conclusion, then invent/manipulate the data until it supports your conclusion.

They suddenly act as if Claude has awarded them with a second PhD in CS. Now they know everything and everything you tell them gets filtered through Claude.

It's like "software dude thinks he can do hardware", but on steroids. They don't know what they don't know and they think they have a panacea in their hands.

Don't you know? Software is beneath them and the fiddly bits are just standing in the way of them getting their BigImportantWork™ done.

Consider whether this is an uncharitable comment --- someone with little expertise in a discipline has made a rookie mistake and didn't realize that the wires weren't produced individually.

Professionals overestimating their knowledge is a very common thing!

Fair, but software engineers are especially known for this. There was an XKCD about it

https://xkcd.com/1831/

What a rancid comment. The first thing you can think of when seeing someone earnestly sharing their learning process, is to insult them of being vain.

He's right about the rest. We software people can definitely be annoying.

All people are annoying. It's still mean spirited in this instance. The author is likely reading all of these comments.

Try working on a software project as a non-developer and see if you still respond so negatively to their sentiment. I can’t tell you how many times developers tried to arrogantly and dismissively explain design principles to me, as an experienced, degree-holding designer, because they skimmed a whole Tufte book at some point.

I was a developer for a decade before I went to school for design, so I’ve seen it from the other side. It’s not all bad: that overconfidence can lead people to tackle problems they’d abandon if they really understood the domain’s complexities. But often it presents like developers acting like their genius developer brain allows them to solve difficult problems in completely different fields with a few glib analogies and a few brief thought experiments.

I don't know, I've had more non-technical people and trades try and mansplain bullshit they don't understand than tech people have.

People tend to overestimate their knowledge of other disciplines.

I have worked with a LOT of PHD's in recent years. Their code leaves much to be desired.

It's called misplaced confidence and it isn't exclusive to software engineers. Doctors, engineers, presidents... The list goes on.

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