Sedan so I can't help you with most of the routing, but my car had a hole with a bolt in it dead center behind the license plate that I used instead of drilling.

 

Interesting, I'll check for that, thanks.

For the red reverse-light wire, am I just looking for whatever goes to the white backup lights?

 

This might be what to not do.

Camera - there's a spot for a factory camera just to the right of the hatch release. I would have liked to attach the camera there as close to center as possible but that requires removing the hatch release assembly and breaking it open to route camera wiring. I had to replace a S210 hatch release assembly and it was an absolute Chinese puzzle. Maybe the S211 is easier but I didn't need to find out. Instead I drilled vertically through the chrome plastic trim between the right attachment screw and license plate light and metal above to get the wire into the hatch. The camera itself shields the holes so nothing's getting into hatch. I put a grommet in the metal hole to protect the camera wiring. A dab of silicone to positively seal the hole wouldn't hurt. Mind the height of the camera's threaded post if it's of that type. The post might extend through the metal as mind does though I threaded the nut against the plastic trim. It's not a level surface under the nut but the camera is mostly held by thick exterior rated mounting tape.

I thought about using a license plate frame camera to have it dead center but it'd be in the way of the hatch release. I could attach it to the bottom center of a license plate frame but I have a modicum of taste

Wiring - an earlier camera had a micro connector which I routed through hinge accordion. I cut a slot in the accordion in the cabin because I didn't want to remove paneling. The current camera has an RCA jack that won't go through the accordion. It comes out the the left hatch pillar liner near the corner then snakes under the weatherstrip to the hinge area. I zip tied it outside the accordion then snaked it above the headliner. There's enough access to work by gently pulling down the headliner. Then I pressed the wire into the seam between the hatch area headliner and D-pillar liner and kept pressing it along the roof seam, over the C- and B-pillars to the A-pillar. It runs down the A-pillar to the fuse box panel then under the steering wheel to the center console. I removed only the driver door weatherstrip to do this.

I chatted with a forum member who ran wiring along the hatch strut into the cabin. I couldn't figure that out without pulling panels.

Camera trigger - I don't have fancy LED tail lights that I can tell. I tapped the camera red wire to the wire that goes to the 12V reverse light bulb. I don't know if S211s have LED tail lights option nor whether that means the reversing light gets something other than 12V.

Sixto
05 E320 wagon 217k miles
99 SL500 69k miles

 

To find the reverse wire put your shifter in reverse (pop off the base of the shifter and depress the black rocker thingy at the base of the lever mount, rear side) and then use an electrical probe on the wire connector (may have to unplug?).

When I installed cameras in my sedans I used relays, connecting a wire from the reverse wire to the trigger pole on the relay and pulling power from a fuse block that's down in the tire well (I had some factory fuse holders and wiring from my parts car). A relay, though it complicates things a bit, isolates add-on stuff from the car's circuitry.

Pretty sure that everything is using 12v (which for standard automotive relays is fine). The amperage draw is likely the only difference and it's the reason why I don't want to really pull power from such circuits as this can present as a bulb failure or such.

 

These are awesome suggestions, thanks everyone for your time & input! I'm moving pretty slowly on this project, basically just spare time on the weekends, so I might not have much to contribute for a little while, but I'll be sure to post some updates & photos when I figure out how I want to do this.

 

Just a clarification on the wiring: you have the power cable for the camera itself with red and black, and then at the end of the video cable (yellow connector for the headunit) there is a small red trigger wire. The idea of the red trigger wire is to connect it to the reverse camera trigger input on the headunit so that the headunit is alerted when the backup camera is active and will switch to the camera feed.

I wired the positive end of the power cable (red) to the reverse lights, and negative end (black) to ground, so the camera is ONLY on/recording when the car is in reverse. The small red trigger wire stays at the front of the car by the headunit and will tell it to switch to camera feed whenever the camera comes on (only in reverse).

Find the wiring harness for the tail lamp, and then you'll have:: Reverse light wires on both sides of the car will be yellow/gray striped, and the ground wires will be the thicker brown wire.

 

Good catch, @Luke81Roberts ! The display also has to be triggered by shifting into reverse.

Most but not all cameras have an RCA jack/red wire combination. Some use a mini plug for video signal and trigger which fits tablet/DVR devices or can be used with an RCA jack adapter. e.g.:

Amazon.com: Epronic 4 Pin Backup Camera for Carplay Screen Monitor Support Mirror Image AHD 1080P Reverse Camera 2.5mm Jack to 4 Pin Front/Rear View Camera, 20ft Male Plug : Electronics

Buy Epronic 4 Pin Backup Camera for Carplay Screen Monitor Support Mirror Image AHD 1080P Reverse Camera 2.5mm Jack to 4 Pin Front/Rear View Camera, 20ft Male Plug: Vehicle Backup Cameras - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

You can snake the inline 4-pin connector through the hinge accordion. Tedious but I've done it. Maybe with judicious application of heat and/or a fish wire and muscle you can get an RCA jack through the accordion.

@DieselBound can help with camera specs. Get as much resolution as the display will support. Flat view is more useful than fisheye. My cameras have acceptable night performance without LEDs.

Aside, I'm adding a switch and diode to our minivan so I can check on the trailer through the camera while moving forward since I can't see it in the mirrors. Diode so the reversing lights don't come on on the highway

Sixto
05 E320 wagon 217k miles
99 SL500 69k miles

 

So here's what happened - I got a nice situation figured out for mounting the display, I used wires to attach it to the center dashboard speaker cover, as shown in this video:

I'm really happy with that, none of the other solutions I tried felt very solid.

The mount itself was a little droopy and bouncy, so I also made a little leather chin rest for it:

I did a little more routing & tucking of cables, but I never got the backup cam routed all the way - BECAUSE I also took the car to a body shop to get some old minor accident damage taken care of at the front bumper, and they took it apart so badly that they say it "won't go together anymore." They totaled it out for $5400 or something, so now I'm the new owner of a 2022 Polestar 2 instead.

Sucks to go out this way, but I do like the new car.

 

Wow, very shoddy work by that body shop!

I mounted my display in the same location, attached to that front speaker cover. I like it very much in that location.