The output of the Alternator on these FORD truck engine electrical systems goes to the "Fuse and Relay box" under the hood, where it is then distributed to the under-the-hood electrical systems such as the headlights, dash AC, etcetera.
There is also a "fuseable link" (or fuse) that is in line with the main electrical wiring that is there in case there is a short in the RV electrical system for safety purposes.
You should use a multimeter and measure the voltage on the output of the alternator (with the engine running) and then on the large hot wire going into the fuse box.
In each case, you should read approximately 13.5 VDC from that contact to the ground.
If there is no output from the alternator, then it is bad.
If there is no voltage going into the Fuse box then there is a wire which is not connected.
If these are OK then you should go to your engine battery and measure the voltage across the voltage terminals and it should read approximately 13.5-VDC. If you read around 12.5-VDC or lower then there it is not getting voltage from the alternator.