When the car is at higher rpms 1500-2000ish (when the car is driving on city streets or highways) everything is fine. Sometimes when the car is stopped and the rpm's are low around 500-1000 the lights sometimes dim and flicker, the head unit even turns off sometimes. Sound like an alternator problem? I'm pretty sure all of the wiring is good with good grounds.

 

How old is the battery?
Have it load tested to see how many cranking amps it has!
Even if it reads decent voltage; you should have this done!!
That could be your problem!!

 

is this something new thats happening?
or have you had this problem for some time
its definatly an alternator problem
either its wore out or you need a bigger one