Here's how to hardwire a dashcam!
This is on a e350 so the fuses may be different for the e53 since its a plug in hybrid

green squares = clip locations
red arrows = which way to pull
teal/light blue line = where to route the dashcam wires

I would recommend wrapping the wires in felt tape before to prevent any rattles later on.

1. Dashboard Side Panel
Shove a pry tool in the gap between the glovebox and trim. Pull towards the right first then pull towards you. The metal clips are very tight and the clips located close to the pillar take some work to remove.



2. A-Pillar
The clip roughly looks like how I drew it in the picture. You have to make sure to push the two prongs on the left and right in after slightly pulling the clip outwards first. Then, while pushing the prongs in from the left and right pull the clip out fully. There is a metal clip attached to the end of the plastic part.
Here's the part number for the clip: 214-692-06-00-1D03 (Gray Headliner)
Make sure to disengage both clips then pull out and up.


3. Door Sill
The door sill has a couple metal clips underneath. Begin by pulling upwards then pulling outwards to remove. Route the wires under the door sill trim and shove it under the B-pillar trim towards the rear.


4. Rear Door Sill
The rear door sill trim cant be removed because it's overlapped with the rear seats. Tuck the wiring under the trim and the gap between the seat.


5. Rear Seat
Fold the rear seat down in preparation for the next step. Tuck the wiring between the seat and trim and then route it under the trim as shown.



6. Trunk
Lift the trunk floor and shove the wiring in the gap between the two panels towards the rear fusebox.



7. Fuse Box
Remove the fuse box cover as shown. With the trunk floor lifted, drill a small floor in the trim and then route the wire through. There should be a bolt near the fusebox in the approximate location shown to use as a grounding point.


8. Fuses
Use the two fuses shown.

 

Nice write-up! Curious what camera system you installed and what the finished installation of the cameras look like?

 

Thank you!
I installed the FineVu X7700 (http://www.fine-drive.com/product/X7700_POWER.do)

here are some pictures

 

Looks clean but
Korean brands I recommend Thinkware and Blackvue.

 

On the front camera how close is the lens to the windshield and do you get any glare from the ambient light at night?