I am currently working on upgrading my head unit to a Joying double din unit, after taking out the old unit which was working perfect as normal, I took out the 3 pins from the connector that's going into the head unit (ground, 12V+ always on and the output signal to the amplifier/assembly in the trunk), I was taking them out to solder the wires that are going to the new head unit into them instead of cutting the wires or slicing them and soldering in the middle of them, so I made a silly mistake of taking out the ground and 12+ at the same time and they touched and some sparks came out of them then the 12V no longer has output.
I know these three wires go back to the trunk into the rest of the sound system assembly and bounce through almost all of the components, I tested the signal (blue wire) and ground (brown wire) for continuity with the others in the trunk and they came back good but the 12V (red/yellow) is dead with all the leads I can find in the assembly in the trunk. but when I test the 12V from the assembly with a multimeter they all give out 12V but no continuity to the front.
So basically my problem is with the wire holding constant 12V from the assembly in the trunk to the front head unit is now dead, any idea how or where I can find the faulty area in that wire ? I managed to connect the new head unit 12V from the A/C wire.

 

Do you have the fuse diagram for the car? It’s a folded piece of paper inside on of the fuse boxes. Usually inside the vehicle.

 

yes I do have the fuse diagram ( the paper that has the location of the fuses and their numbers and functions if that what you mean) but I want to follow a wire and I can't find a diagram for that.

 

Has anything else failed? Is it just the live supply to the head unit? I blew the megafuse by the battery once - car wouldn't start. I was in a bit of a panic until I found the remains of the 100A fusible link I had managed to melt

 

I didn't drive the car out yet since then but I turned it on for like 30 minutes and didn't see anything wrong, I haven't installed the dashbosrd yet in. I will install it later just need to finish installing the new usb outputs from the head unit and I will try to see if anything else isn't working, the whole MOST system in the trunk is working though.

 

I found this online and it turns out I misread the fuse diagram and checked F20 not F22 (don't know how) I replaced F22 (7.5 amps) and power came back in the live (12v+) wire to the head unit.
Thanks everyone for your responses

 

Just realise you fixed it! Yay!

 

🥳🥳

 

Hey Adlianooo, I am preparing to do the same job. Did you connect the new unit to the canbus network of the car? If you did, where did you make the connection?

 

I didn't yet finish that part, it turns out I need one of those fiber optic decoder that contains CANB-L and CANB-H cables to be connected to the CAN BUS hub in the vehicle and I am still looking into more details for that.

I ordered this part "https://www.ebay.com/itm/For-Mercedes-Benz-CLS-E-S-E-W211-AUX-Optical-Fiber-Decoder-Box-Amplifier-Adapter-/254450145479?_trksid=p2349624.m46890.l49286" and waiting for it to arrive and try it instead of the other one that I got that doesn't have CAN BUS cables in it

If you looked into W220 forums you should find another gentleman who was able to do that to his S-Class (W220) and he gives alot of details I will attach below one of his PDF files that he shared on the forum (somewhere I can't really find it again tbh)

Good luck in your journey and let us know how it goes, I will definitely give more info when I finally succeed since I have done some other upgrades to the center console.

 

Yeah I ran in to the same problem checked all the fuses and still have no power . Bypassed it for now .but will double check at first light . To see off 22 is the issue. Thanks

 

check fuse F20, under the hood driver side fuse box.