Complete vehicle harness, except engine. Rodent damage on a new 760i. Bags are full of the wiring/connectors that get pulled through firewall/trunk/rear openings to prevent damage.
this post was submitted on 25 Feb 2026
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How long did it take for the parts to come in?
I bet you learned a lot about the car, but whether you wanted to is another story.
BMW design has had better times.
Complete body harnesses are all custom made to order only depending on options, so it takes a couple months to get one.
That’s what I’ve heard. Lots of work!
I still don’t understand why they’re so expensive? They’re just different lengths of wire.
I want a rear door harness for my Land Rover but it’s like £230 and it only hooks up a wiper and central locking.
This harness is $16,500.
Blimey!
- Copper expensive.
- Wiring harnesses rarely fail/need to be replaced, which makes it a niche part.
- Even though they probably have warehouses full of spare wiring harnesses, oem manufacturers like to jack the price up because they know people will pay it - in particular, insurance companies don't want to get sued/blamed/bad reviews for installing inferior third party parts, and so will pay whatever it costs to get OEM. Same with many mechanics.
- Aftermarket manufacturers, since they do tend to only manufacture the number of parts the market demands, do not benefit from economies of scale like OEM manufacturers, and will have much higher manufacturing costs per part for every step in the process. And since the OEM part is so expensive, they can still make a tidy profit selling a part that is less expensive but still quite expensive.
- It is typically very easy to replace any damaged wiring with generic wiring and connectors which are available for pennies at any auto parts or hardware store. So the people who are willing to pay the premium for OEM or OEM compatible wiring and connectors are typically also the sort of people to get sticker shock, shrug, and say "damn! Well, guess that's how much it costs." Or else they are "just so" people who absolutely must have exactly the right part on principle, even if it costs an arm and a leg.
“5) It is typically very easy to replace any damaged wiring with generic wiring and connectors which are available for pennies at any auto parts or hardware store.”
Not so much anymore. A large percentage of critical wiring is now “low resistance” circuits. They are very sensitive to resistance. That means we are only allowed to make a single splice per wire along its full length. So if a section of wire is missing, the entire wire must be replaced from end to end with new terminals. Those can sometimes be the full length of the car.
Huh. TIL.
I'm not an electrical engineer, but there's manufacturer recommendations and there's "good enough for the job". If I bought that car out of warranty, and had to splice a wire, would it actually matter? And if it did, couldn't I just... use a thicker conductor and some high quality connectors?
Upping the size of the conductor adds resistance to the circuit. The wiring in those harnesses are like 20-26 gauge. When you're sending a signal (rather than just supplying power) that extra resistance causes all kinds of problems.
If you're making a repair with low resistance wiring, it's pretty much standard practice to solder in a repair wire of the same gauge and conductor type. A butt splice will also add resistance to the circuit.
You can do a lot of things with power feeder wiring that you can't with low resistance signal wiring.
You can absolutely use a larger wire (lower gauge) and high quality splices to get a repair that doesn't add any significant amount of resistance for this use case.
If your wire diameter is larger then your resistance is lower, not greater (so 18-24 awg in your example, or equivalent in mm). Then you use low resistance splice methods, not a shitty Amazon butt splice.
Not sure where you're coming from. "Replace the entire wire" is the knuckle dragging, high labor cost low technical aptitude solution.
If a rodent chewed through a ton of wires then yeah, you're replacing the whole thing because it's not cost effective to look for every nick and chew and patch them all. But a single short or nick? You can totally patch it, and saying otherwise just isn't facts.
Wait how would upping the size add resistance? It should reduce it
When you are dealing with high frequency signalling like that you introduce signal reflections when you change the geometry of the conductor. If you don't account for that reflection in a design it can interfere with the signalling and introduce enough noise to stop reliably working. Splices that aren't soldered connections to the same size of wire will all add just a bit of resistance, regardless of their size, and even solder will change the transmission profile of the wire slightly at high frequencies.
Copper isn't that expensive. $6/lb = $480. Equivalent weight in Romex would be ~$700. $900 for shielded Cat 6.
They’re handmade, apparently. Drives up the cost significantly, well beyond material cost. We’re pretty used to mass produced parts and wiring harnesses aren’t mass produced after the production run.
I still don’t understand why they’re so expensive?
To answer the question as written: Correct. You do not understand why they're so expensive. I'm very confident in this answer because I see you said as much, and you're the authority on what you understand.
Glad I could answer your question as written. It feels good to help.
Coworker once had to do the same on an E60. Harness weighed 600 lbs and required an engine crane just to put it in the vehicle. We have come a long way.
Ever since you worked on it...
If only there were a few connectors to seprate that into multiple sections. Having to replace the entire harness suuuucks.
German engineering.
If someone mentions maintenance costs during the design process they are immediately dragged out and shot.
First fast then good
Just curious if there's a way from preventing this in the first place?
I had a bunch of mice build a nest in my ductwork in my car last year. I screwed down a metal grate over the cabin air inlet, got one of those electronic rodent repellents and zip tied it under the hood and change the batteries every week. I also got a plastic bin that I park over and throw the rodent repellent balls in there periodically. It was $2k for them to fix it and I don’t want to spend that again. Also curious if anyone has any other ideas.
I had a car that was often hit by rodents. I got some LED light strips and taped a couple of them under the hood, and wired them to the battery with a fuse. It seemed to work.
Could you add lithium cells to that repellant and charge from the car battery? Using some 18650 batteries and a usb-c lithium charger hooked up to the accessories power would probably do the trick. Unless you use the car infrequently / power draw.
Lithium chargers are cheap as chips via aliexpress, just depends on the input voltage to the repellant device & how much power it draws. You could probably add an esp32 to that setup to report back if the charge is falling too low if you really wanted to get invested 😅.
Be careful with that. Have seen battery packs like that stuffed under dashes that have exploded.
Yeah, I think you can buy a repellent that hooks to the car battery, but I use the car somewhat infrequently sometimes and didn’t want to risk a parasitic draw on it.
I doubt this product is installable with an already-installed electrical harness, but Techflex makes rodent-resistant sleeving. It's probably coated with a chemical the animals don't care for.
Honda has a tape like that that is rodent resistant. It contains capsaicin.
Thanks, I'm gonna go chew on some Hondas now