Nissan Repair: electrical problem, amp meter, internal regulator

Question
I recently had a new alternator and battery installed in my 96 I30 infiniti but
the dash lights and headlamps will still dim drastically when I step on the
brake or when I first start to use the power windows. They will instantly fade
back up but this is how it started acting and slowly got worse till it just died
one day. At idle with the headlights and radio on (plus an XM radio plugged
into the cig lighter) I get 14.3 volts at the alternator but only 13.1 at the
battery. don't know if that means anything but I thought it was interesting
and might help. Any Ideas?

Answer
Paul,

Sounds like the internal regulator on the new alternator is defective.  When a load is applied to the system the alternator is supposed to crank out more amps.  You could get an inductive amp meter and see what is going on or take it to Autozone or Checker and they will do a system check for free.  Be sure to duplicate what you are doing like rolling the window up or down or apply the brake to give them the full picture when they do the check.  They bring the unit to your car in the parking lot so you just have to drive down.