Nissan Repair: Electrical, heater blower, electrical inspection

Question
When I turn on the headlights (which are kind of dim) my radio will go off, the wipers slow down, and the heater blower slows down. I had the battery and alternator checked and both checked out ok the guys at the parts store said it might be the voltage regulator, could this be what it is? They told me the amp reading which was 3.9 was a bit high.
Thanks,  Shawn

Answer
Shawn,

THe voltage regulator is in the alternator so it will have to be removed to replace it or just replace the alternator.  If that is the case.  Now, I would see if the headlight switch or relay is dragging down the electrical system.  It seems so since you say things are good when the headlights are off.  GO to Autozone or Checker and get a free electrical inspection with and without the lights on and see if the alternator and charging system are working properly and then you should know for sure.