Where To Run Power Wire On 2016 Mercedes GLE-350 For 7-Way and Brake Controller

Updated 06/04/2020 | Published 06/03/2020

Products Featured in This Question

Curt Echo Wireless Brake Controller - 7-Way Plug-in w/ Bluetooth App - Up to 2 Axles - Proportional

(1915)

$289.95

7-Way RV Upgrade Kit for Trailer Brake Controller Installation - 12 Gauge Wires

(393)

$91.91

Question:

I am hooking up a 4-way to 7-way trailer adapter for my 2016 Mercedes GLE-350. Part of this process involves wiring up a direct 12V connection to the battery through a breaker to provide power for the trailer brakes. I am wondering about the requirements for how this is wired. The Mercedes has kind of an odd battery situation. There are actually two batteries, a primary under the front passenger seat and an auxiliary in the trunk area. The primary battery is very hard to access especially the positive terminal, but it wires very closely by to the primary fuse box, via a large cable not sure the AWG, but its big. Im wondering if: 1 is it possible to connect to the auxiliary battery instead of the primary to provide brake power? Im guessing not since it is smaller, but am not sure 2 if I cannot easily access the positive terminal of the battery, could I hook onto the lead where the battery connects to the fuse box? As far as I can tell, it is a straight connection from the fuse box to the battery, and its a large diameter wire so I think it would be the same. Attaching a photo of that fuse box for reference. Where Im talking about hooking in is the red screw-down connector at the top of the photo.

asked by: David H

Expert Reply:

If you need to install a brake controller on a 2016 Mercedes GLE-350, I recommend the wireless route and the best option for this is the Curt Echo Wireless Trailer Brake Controller part # C51180. In order to use the Curt Echo you'll also need the ZCI Circuit Protected Vehicle Wiring Harness part # 119250KIT and 7-Way RV Upgrade Kit for Trailer Brake Controller Installation part # ETBC7L.

In order to install the above components you'll need to run two wires to the positive battery terminal, one for the 4-way and one for the 4 to 7-way adapter. In regards to which battery to use, I must recommend the primary battery as I really don't have any specifics on the battery specs for your vehicle. That said, I don't see any issue attaching to the plate on the fuse box instead of directly to the battery terminal.

expert reply by: Conner L