Head unit wire extender
 

Does anyone has made a wire extender for the head unit main harness?

I mean, I changed my head unit for a tesla style one, and it picks the audio from the main harness, but I want it to pick the audio from RCA, so Im thinking about make a harness extender for the stock one, using a Metra 70-7553 and a Metra 71-7552.


So then I could plug the tesla unit into the harness, and the RCA to the head unit keeping the stock bose amp and using it by RCA. All of this is because I'm getting a hissing noise which I think is coming from using amplified signals into the bose amp, so maybe going by RCA it goes away.

Do you think it is doable? Am I missing something? Does the metra come with enough pins to wire everything?

Apologyze for my english.

Which Tesla style unit do you have: AuCar/NiftyCity, Brainiac, or something else?

I have NiftyCity one.

Already did my research and ordered 3 Metra harnesses: Metra 70-7553, Metra 70-7552 and Metra 71-7552 for the male one.

I ordered 3 because the metra 70-7553 lacks 3 pins that I will need in order to get everything working, so I will take the 3 extra pins from the 70-7552.

Checked AV manual and made a diagram, also checked that diagram with my car and it matches. So once the harnesses arrives it should be pretty straightforward.

Here is the diagram I made in case someone is interested:
https://i.ibb.co/JFGtGx5/conector-radio2.png

By this approach you can wire as u want without cutting any OEM harness on your car.

I'll post more pics and results when everything arrives (It will delay a bit since Im ordering to USA from Spain).

My only concern now is what is "shield" wire doing, and if I can extend that one aswell as a normal wire or just omit it.

Shield wires are typically grounded to keep electrical noise off the other wires from things that emit emi.

I’ll be watching this and the other thread as I’m having a somewhat similar issue.

Received the harnesses today. Wired everything up and seems to be working, I will test it a bit more and post more details.

Okay, I tested it enough and I can say that it's working as expected.

I removed the audio decoder box that came with my nifty city tesla screen, and replaced it with the harness I made. After replacing it and wiring the RCA to the tesla unit, the sound went back to it's normal volume before the install, also the hissing noise that I had is gone using the custom harness.

For the wiring, I used the pinout posted earlier in this thread.

I tin soldered the connections between wires and tapped it with heat shrink sleeve.
https://i.ibb.co/DfV3DZg/IMG-2194.jpg

To remove the pins, there is a tiny hole in each pin, I mean, each pin has 2 holes, one for the connection, and another one tinier, which is for unlocking that pin out, so you can gently insert a small tool on that hole and pull the wire with the pin out.
I used this tool, which is for removing pins of PC power supply:
https://i.ibb.co/9Y8r0JW/IMG-2196.jpg

After that, and according to the pinout, I removed every wire that was not needed in Metra 70-7553 and 71-7552. Took the extra pins from the Metra 70-7552, because Metra 70-7553 lacked some pins that were needed for steering wheel controls.

Also removed the audio pins from the Metra 71-7552, because the audio is wired to the RCA from the tesla unit.

Here is the harness finished:
https://i.ibb.co/hKXbyFY/IMG-2198.jpg

And here how it should be wired:
https://i.ibb.co/ymTJYCZ/IMG-2199.jpg

I finally wired the shield wire like a normal wire, no issues.

If you have spare audio decoder box and you dont mind breaking it, you can do everything with only the Metra 70-7553 and take the male connector and the rest of the pins from the decoder box.

Note that this worked for my car (2019 Nismo with factory NAV), but I checked the pinout on the AV manual, you should check yours before doing anything, I am not responsible for any problems someone else may have with this wiring, and this post is for informational purposes only.



Hope it helps.

Thank you for this post makeao! I haven't had the hissing issue but, I did make a custom harness to go back to my amp and spare tire sub and then back up to the car harness and new speaker wires. Everything works great EXCEPT for the steering wheel controls. I can see now that I probably didn't connect pins 6, 15 and/or 16. I shouldn't be too bad popping out the tablet and testing/fixing it!

I'm glad it helps. Remember that if you are using Metra 70-7553 or Metra 70-7552 you should look at the pinout in this thread from wire side, not from conector side.