The solar prewires are one green and one yellow wire labeled "solar" that are bundled in with a bunch of wires affectionately know on this forum as the "rats nest". Here is a picture of how I installed my solar controller to the solar prewire on a 2017 FC25FB. You can see the 10 gauge green and yellow wires in the picture, and if you look closely at the floor in the top-right corner picture you can see the "rats nest". http://www.airforums.com/forums/atta...0&d=1539352234
The rats nest was in the front curb-side corner of my Airstream directly below the positive and negative bus bars.
You can see and read about my solar installation, and from many others who showed off their systems in the "Solar Show and Tell" thread: http://www.airforums.com/forums/f448...ll-181608.html
2018 Globetrotter 27Q, 36 nights 5,235 miles, 600W Solar - Produced 50 kWh, PD4655L, 6V Batteries, Champion DualFuel, ProPride, 16" tires, 2019 F250 PSD
Sold: 2017 FC25FB, 316 nights 40,150 miles, 400W Solar - Produced 200 kWh in 216 days
2013 Casita SD17 89 nights 16,200 miles