My car radio doesn't remember anything.

Thank you to everyone who mentioned the swapping of the red and yellow wires because I was able to fix the problem with my two cars (C2 and Ford Galaxy) because of that.

Problem solved! I managed to switch the two red and yellow wires.

Thanks everyone for your help :)

The yellow wire must not be connected or poorly connected; it needs to be constantly powered at 12v, so directly not to the ignition on the contact
on your old car, the connection was correct, don't complicate things unnecessarily....

red and yellow wire inversion

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Kenwood KDC- 4754SD
MTX TH904 > woofer MTX T8652 > MTX road thunder
Alpine V12 MRV-F305 > tweeters MTX T8652

Hello

It's the yellow wire for the memory, it must always have +12!

Hello, I had the same memory issue with my device and reversing the red and yellow wires works perfectly

thank you for allowing me to solve my problem in 2 minutes flat :D

Thank you everyone for talking about the subject, I was able to solve the problem with my Opel Astra ☺

I don't know enough, but from the beginning I submitted to you the most likely hypothesis: wiring error at 80% precisely because I don't know enough about automotive electricity, I didn't dare go higher..

Idea taken up and confirmed by racegame who seems confident,

So the most logical solution is that on the old car, it was wired correctly, but not on the new one
It doesn’t matter who did the wiring, you’re a pro, we don’t know,
So don't take offense; we’re not judging anyone; "someone" made a mistake, that’s all, we can’t elaborate further without seeing in person how it looks
We can only make you understand to check or have your wiring checked..
Do you understand?, and let us know the solution you find when it works again.

Come on, have a good night.

Hello
I would say it's 80% about the wiring... there must be a wire that is not connected or is connected incorrectly.