4 ms·

> 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 harnes

> 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-au/air/GUID-69EED053-DAD4-40B0-BCFC-B789B96D479D.html https://service.tesla.com/docs/Model3/ServiceManual/2024/en-...

entropie 7mo ago
> 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).
- kube-system 7mo ago
  That's what I figure -- but it was wild to read that after reading the part about component-level PCB repair lol
- trebligdivad 7mo ago
  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.
MBCook 7mo ago
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.
- kube-system 7mo ago
  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.
  - msisk6 7mo ago
    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.
    - kube-system 7mo ago
      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
      - yearolinuxdsktp 7mo ago
        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.
    - yearolinuxdsktp 7mo ago
      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-manual-hardware?r=1255086 https://www.renesas.com/en/document/mah/rh850e1l-users-manua...
spuz 7mo ago
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.
- deleted 7mo ago
  [deleted]
- kube-system 7mo ago
  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-au/air/GUID-9231349B-F470-46AA-ADA4-579A0AFEA12B.html https://service.tesla.com/docs/Model3/ServiceManual/2024/en-...
- longislandguido 7mo ago
  [flagged]
  - fortran77 7mo ago
    Why are you so hostile towards someone who's experiment with an interesting computer? What's wrong with you?
longislandguido 7mo ago
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.
- EA-3167 7mo ago
  There's a reason that John Salvatier's 'Reality Has A Surprising Amount of Detail' blog entry is so evergreen on this forum.
- acuozzo 7mo ago
  > 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.
  - juleiie 7mo ago
    What happens?
    - incrediblylarge 7mo ago
      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.
      - zer00eyz 7mo ago
FireBeyond 7mo ago
> 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.
- cluckindan 7mo ago
  Tesla treated the service manual like congress treats certain recently surfaced files.
- creantum 7mo ago
  Wrong. They’ve always been open, even with their patents too. All free to use, no royalties
  - FireBeyond 7mo ago
    Confidently incorrect. https://www.reddit.com/r/teslamotors/comments/utivlj/tesla_service_manuals_are_now_free_get_yours/ https://www.reddit.com/r/teslamotors/comments/utivlj/tesla_s... > This used to cost $3187.50 https://driveteslacanada.ca/news/tesla-service-manuals-free-again/ 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-manuals-are-free-again.22533/ 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").
moomoo11 7mo ago
I'm sure you're an expert, pro at everything.
- NamlchakKhandro 7mo ago
  Yes I am. Thankyou for recognising that
- kube-system 7mo ago
  I wasn’t criticizing them.
Onavo 7mo ago
EVS have actually managed to reduce the number of wire bundles (mostly due to switching to Ethernet instead of CAN Bus)
- jandrese 7mo ago
  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.
- shibapuppie 7mo ago
  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.
  - BenjiWiebe 7mo ago
    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.
mschuster91 7mo ago
> 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 https://de.wikipedia.org/wiki/ISO_10487
yardie 7mo ago
I was more fascinated that a new wiring harness was $80! I've easily spent $30-50 for a single VAG cable 1ft pigtail.

entropie 7mo ago

> 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).

kube-system 7mo ago
That's what I figure -- but it was wild to read that after reading the part about component-level PCB repair lol
trebligdivad 7mo ago
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.

MBCook 7mo ago

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.

kube-system 7mo ago
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.
- msisk6 7mo ago
  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.
  - kube-system 7mo ago
    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
    - yearolinuxdsktp 7mo ago
      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.
  - yearolinuxdsktp 7mo ago
    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-manual-hardware?r=1255086 https://www.renesas.com/en/document/mah/rh850e1l-users-manua...

spuz 7mo ago

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.

deleted 7mo ago
[deleted]
kube-system 7mo ago
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-au/air/GUID-9231349B-F470-46AA-ADA4-579A0AFEA12B.html https://service.tesla.com/docs/Model3/ServiceManual/2024/en-...
longislandguido 7mo ago
[flagged]
- fortran77 7mo ago
  Why are you so hostile towards someone who's experiment with an interesting computer? What's wrong with you?

longislandguido 7mo ago

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.

EA-3167 7mo ago
There's a reason that John Salvatier's 'Reality Has A Surprising Amount of Detail' blog entry is so evergreen on this forum.
acuozzo 7mo ago
> 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.
- juleiie 7mo ago
  What happens?
  - incrediblylarge 7mo ago
    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.
    - zer00eyz 7mo ago

FireBeyond 7mo ago

> 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.

cluckindan 7mo ago
Tesla treated the service manual like congress treats certain recently surfaced files.
creantum 7mo ago
Wrong. They’ve always been open, even with their patents too. All free to use, no royalties
- FireBeyond 7mo ago
  Confidently incorrect. https://www.reddit.com/r/teslamotors/comments/utivlj/tesla_service_manuals_are_now_free_get_yours/ https://www.reddit.com/r/teslamotors/comments/utivlj/tesla_s... > This used to cost $3187.50 https://driveteslacanada.ca/news/tesla-service-manuals-free-again/ 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-manuals-are-free-again.22533/ 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").

moomoo11 7mo ago

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

NamlchakKhandro 7mo ago
Yes I am. Thankyou for recognising that
kube-system 7mo ago
I wasn’t criticizing them.

Onavo 7mo ago

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

jandrese 7mo ago
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.
shibapuppie 7mo ago
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.
- BenjiWiebe 7mo ago
  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.

mschuster91 7mo ago

> 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 https://de.wikipedia.org/wiki/ISO_10487

yardie 7mo ago

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