Anyone know what wire color goes to backup lights so I can tap into it to power backup sensor unit? Pulled panels on lift gate and wire color going to backup light is Solid Yellow (assumed power) and Solid Black (assumed ground). Tapped into these wires in sidewall wiring bundle but no power when backup light are on.

Any Ideas on which wire powers backup lights?

Thanks

 

I'm going to assume you have the right wires (I don't know without looking them up on a diag!). If so, you'll probably need to use a relay to power up anything. MBs like to throw a code for any extra power consummation, of most circuits... better to power whatever through a relay, fuse hooked to 1 of the batteries. If you're not sure on what to do, visit a car stereo shop or any auto electric business to set you up. You'll probably not get enough juice from the lighting circuits as they are low voltage LED lines with pulse modulation for most lamps.

 

I thought I had the correct wires, same colors on backup light on liftgate socket, but when I checked for voltage on the wires in the wire bundle in the spare tire area there was no voltage! So I need to know which wire pare is correct in the bundle. Also the backup light is incandescent 12v bulb not LED, so I don't think I need a relay but will consider that because I can power unit from Aux 12v in rear compartment easily. I just need to power relay from backup circuit. So any ideas would help. Also need to know if anyone has drilled through rear bumper and did you have to remove it first?

Thanks for replies

 

OK... thinking back to my GLK(2011). I installed a rear camera and used the 'incandescent' backup bulb wire to activate the camera. It worked but was constantly throwing blurry lines across the led screen. Adding a relay supplying a solid 12V to the circuit>screen fixed the problem. I believe MB uses 'pulsing' to achieve & monitor circuits to its computers. I'm not sure but my guess is that each circuit will be getting less than 8V in a modulating pulse feed. I may be way off in describing this, but a relay receiving the pulse, and delivering a solid 12V batt fixed my issue, without setting any idiot lights off! Also, try another proper ground, as the black wire may be part of the pulse system.

 

Thanks for the info. I tried to get some kind of voltage off the "yellow wire" (that runs from the bundle in spare compartment through rear post, out lift gate to the backup light socket on the lift gate) in a splice in the spare compartment with connecting to a ground point in the rear post area, but no luck. I will attempt to get a wiring diagram from my mechanic this weekend. Will also ask about using relay.

 

May I ask what parking sensor kit you are using and did you drill the bumper to install the sensors? You could use a relay, use the backup lights to trigger the relay and then 12v source from the 12v supply in the cargo area.

 

I got the kit on ebay. Searched for MB model and color. It was from China, $25, I checked it out and it works fine. So now I am trying to find the correct wire in spare compartment to tap into to power the relay. I will tap the 12v supply for the power to the unit.

I have not drilled into the bumper yet, waiting to make sure i get the power/relay items working first. I am thinking I will have to take bumper off to properly drill out holes for sensors. Other threads on other models have shown that the bumpers are pre marked on inside for the sensor drill holes.