i would have to say its got a broken wire at the alternator as these are so common and working for ford they do a replacement connector and tiny part of loom so it can be replaced.ill get the finis code for it for tomorrow if not fixed.alternator is located on drivers side of engine compartment.if can be seen from the front with bonnet up as there is a gap on the indicator part of the headlight.
the fact the battery is showing 13 or so volts is due to the smart charge system going into back up mode and causing the engine ecu to default to this voltage as it cant see an output from the alternator
hope that piece of waffle helps
