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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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!
“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.
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.
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.
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.
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.