W126 LED Third Brake Light Install - Wiring Help
 

I purchased an LED third brake light bar from ebay after seeing how nice it looked on another members car here..but I can't figure out how to run the wiring into the trunk without drilling a hole in the back shelf. And I can't find instructions on how to remove the rear seat back to do this. Any suggestions please? I live in a area filled with dumb drivers so I need all the brake lighting I can get. Thanks!

You can't wire it to the existing third brake light?

Maybe not standard on a Euro '85.

Sixto
83 300SD can be yours
98 E320 wagon

Ha, didn't see that. Drilling it is.

Yes I can..but what I'm trying to figure out is how to run the wire into the trunk area to do so without having to drill a hole in the back shelf area.

You are correct, sir. I'm trying to keep these crazy drivers from plowing my rear end..especially since these euro models are harder to find..so I'm hoping I can somehow find a space to run the wiring into my trunk area without damaging or drilling anything.

Does your car have reclining rear seats? If so, my SDL had those but I don't remember how they come off, which they have to to replace the rear shocks. If not, there's a tab at each end of the seat cushion where it meets the carpet. Slide the tab towards the door while lifting the forward edge of the seat cushion. Pull off the seat cushion and set aside. There are 3 screws that take an 8mm socket holding the seat back - one at each lower corner, one under the center armrest. With the screws out, lift the seat back about an inch to clear the hangers along the shelf then pull the seat back forward and free.

If you're mounting the brake light along the lower edge of the windows, you might be able to run the wires under the shelf liner towards either door so you can tap into the brake light wires that run under the door jambs then under the seat cushion before going into the trunk. I don't remember how the shelf liner comes off and I think it depends on the speaker arrangement. You might have to remove the sail panels which will be brittle and delicate at this age.

Sixto
83 300SD can be yours
98 E320 wagon

Thanks for all the info. My rear seats do indeed recline..but are not doing so right now..and I haven't asked my mechanic why out of fear of an expensive repair..lol..plus..I normally don't have anyone riding back there anyways. I may just give this up since it is becoming obvious it is not an easy thing to do without possibly damaging something or drilling.

Hmm... it looks like you can tuck the wire in the channel between the shelf liner and the window. Run the wires towards the left b-pillar then floss it between the speaker grill and sail panel. Tuck the wire between the seat back and wind lace all the way to the floor. Pry off the door jamb liner to get to the brake wires to the trunk. No drill, probably just a putty knife to push the wires beyond sight. Look for the wires that match the color of the wires at the brake lights.

Sixto
83 300SD can be yours
98 E320 wagon

I'm going to bring this up on my phone so I can take it with me to my car and see what happens. Hopefully the door jamb liner won't be too brittle..but if it looks like it is I won't even try because it's really hard finding replacement parts for this car..especially the little things. Thanks again!