Jim.....Look at this wiring kit from
etrailerI'm big on wiring my vehicles myself, but often these kits make life simple for a few more dollars. Two things you need to be aware of. First, check to see if the brake lights on the Saturn come on when the vehicle is off (as if it's being towed). The reason for this......if you wire in diodes to operate the Saturn's lights, the brake lights on the Saturn (if they come on when turned off) will override the turn signals if you are stopped at a signal or applying the brakes.
Second, your coach comes with a simple 4 wire system, left/brake, right/brake, running and ground. Your Saturn with separate turn signals will not function with the simple four wire system. You can wire it so that the brake lights on the Saturn can also be the turn signals, or by a converter that converts your simple four wire to basically a six wire, which will decipher between brake and turn signal and allow you to use the Saturn's turn signals and brake lights separately.
Freightliner uses fuses for the left turn, right turn and brake lights. You need to find those and make sure they're good. On my Freightliner, there is a fuse box adjacent to the starting batteries.
Side Note:....When I owned my Monaco, over the years I knew/learned where all the 12 volt fuses were located (3 different areas). When I bought my Dutch Star 2 years ago, I decided to find the fuses and document them. I located four different areas where they had placed 12 volt fuses. I photographed them and then documented them by name/use in a Word program. I keep the photos and description in a note book in the coach. When I need to find a fuse, I look in the book and go straight to that part of the coach.