Your symptoms do not include any information about your motorhome, but let's assume you have one with standard wiring.
SO, first of all, if your motorhome has a FORD (or whatever vendor) drivetrain, then your chassis wiring will be the same as it is with that manufacturer's trucks. This includes the wiring for the signals, brakes and tail lights.
If you have a 2015 motorhome with a FORD drivetrain then it will be wired just like the standard 2016 Ford truck. If nothing else works, you can take your motorhome to your local FORD truck service center.
But, before you do this, you should find the connections to the signal light blinker module, the brake light switch, and the tail light fuse under the dash of your motorhome. Also, there should be the appropriate fuses in the fuse panel under the hood of your motorhome.