Hello,

Just picked up an 2003 E350 and need to tow with it. I am attempting to install the 7 way plug with trailer brakes. I have found a factory 4 plug under the rear bumper and followed it back to a connector with only 4 wires connected. where can I tap into the other wires?.

Under the steering wheel I have found the plug for the brake controller.

Can some one guide me on how to install the 7 plug?

 

Welcome to the site.

The factory brake controller 6 wire connector s/b to the left of the column, coming out of the harness trunk.
For ID,, Connector color is brown,, Wire colors should be,
DB, BK, LG, LG?, LB/BK, BN
Is that the connector your viewing?

Look at the left/rear frame area, s/b 2 connectors there, both black, one will have your 4 connector harness plugged in.

 

Thanks for the reply. Please see attached images.

Picture of 4 way plug, picture of connection after following 4 way plug up the frame, and picture of brake controller connector under dash/steering wheel.

I would like trailer battery charge.

 

All necessary fuses are present in fuse box under the hood as well.

 

Correct on the brake controller connector.

I'll send you a couple of connector/ location views, there should be 2 trailer connectors towards the back. They'll give an idea of wire color, connector configuration..

 

Any chance you could post those views here. I'm looking for the same info. Have factory 4 wire tow package. Want to convert to 7 wire. Know where 4 wire harness plugs in the main harness drivers side rear, but don't know where the power/E-brake signal connector is.

Thanks!