Alternator charge ? 2015 VW Jetta tdi

Was looking put after market stereo in my 2015 Jetta TDI. They sound place told me Jetta run 12 volts I can't see a diesel running 12 volts. How many volts does a Jetta TDI 2015 run I'd imagine 13.4-14.1 right ?

I would tell that place to stick to sound systems, LOL. And the fuel type has zero to do with the electrical system.

All modern Volkswagens run a regulated 14v system, but it can vary a bit... depending on demand. ~13.8 to 14.4 volts while the engine is running seems to be within the normal range. Much of the car's sensitive electrical bits have their own regulating mechanisms, like the lights for instance.

12v battery nominal is 12.6v. That translates from 2.1v per cell. Obviously there can and will be some slight variation.

They still consider this a "12 volt" system instead of a 14 volt. Same as most any other modern car, nothing strange about it.