I've noticed lately whenever I lower my windows or turn on my AC all my lights dim for a split second. This also occurs when I have my turning signal on, every time they blink the lights dim, its pretty annoying.

I'd check the battery post connections, Mine have been known to loosen up from time to time, also does your volt meter jump around when this happens, pickup starts ok? any more info. Jim

Yes, the voltage does drop slightly when doing those actions, The truck starts perfect

I assume the truck is running when all this occurs. It does sound like you may have alternator problems. Something as minor as a turn signal should not be drawing enough current to pull your voltage down. I would monitor the voltage across the battery with the truck running to see that it is being charged (should be about 14.5v) and then turn on the turn signal or other electrical load and see it the voltage is varying. I will stand corrected but I don't think it should if your battery, alternator and voltage regulator are working properly.