I just changed the alternator and now the radio isn't working. I've read it could be fuses, or some sort of anti-theft system that needs an input code. Any advice would be appreciated.

 

Need the Year of of Ranger?

No code, Ranger Radios never had that
Yes, blown fuse, need year to tell you where to look

Also is it a stock Ranger Radio, Ford model?

There is no connection between radio and alternator in any year
And when key is on and engine is off, the alternator is also off, 12volt power comes from battery only, no alternator connection

 

It's a 2001 3.0 V6. with a Stock radio.

 

Here is the 2001 Radio wiring diagram: https://www.therangerstation.com/tec...dio_Wiring.pdf

Fuse 28 is just to MUTE the radio when starting the engine
Fuses 20 and 29 in cab fuse box power the radio