We have a 2019 Scamp 13 (took delivery December 2018) with electric brakes and Autowbrake controller installed by Eveland.  The problem is the trailer brakes were locking up the wheels, and dragging the tires on the road.  With help from the Autowbrake technician, we made sure the controller is on the lightest setting.  The trailer brakes are still a bit grabby at <10mph, and the trailer tires lock up at >15mph.  The Autowbrake tech thinks the controller is connected to the trailer battery instead of the tow vehicle's lights, and that the trailer battery has a bit of a low charge (thus causing the brake performance issues).  He recommends disconnecting the brake controller's black wire and connecting it to the wire powered by the lights. 

My question: Which color wires are for the tow vehicle & trailer lights?  We'd like to resolve this before going to Yosemite (yes) tomorrow.  Failing that, I would need step-by-step instructions how to use a multi/voltmeter, because I don't really know how to use one.  Or:  Should I just start disconnecting/reconnecting wires under the front bench to see which one causes the trailer lights to go out?

Follow-on:  I looked at the Scamp Owner's Manual online, and acc. to page 12 the Green wire is for the tail and marker lights; Red is for the left turn and brake light; Brown is for the right turn and brake light; and Yellow is for the backup (reverse) lights.  Also, Blue is for the electric brakes.  So, which one do you think it is??

N.B.:  The wiring schematic seems to indicate the Green wire goes to all the lights.  Is that it?