Chevrolet Repair: electrical, gmc sierra, feed source

Question
I own a 2005 GMC sierra crew cab 4x4 5.3L.  I am original owner with 24,000 miles and well taken care of.  At times I will check the windows to make sure they are up all the way.  When you do this, the lights in the dash dim.  Just yesterday I accidently did both back windows at the same time and the dash lights dimmed competely out just for a flash.  Also a brake service soon message came across the info bar, but then immediately went away and everything is fine.  Why does it do this?  Thanks for any info.

Answer
HI LANDON,THIS SOUNDS TO ME LIKE SOMETING IN THIS CIRCUIT IS LOOSING POWER FROM A MAIN FEED SOURCE FROM THAT CIRCUIT..SUCH AS BAD CONNECTION OR SOMETHING LIKE THIS..THE LAST POSS PROBLEM IS [MAYBE] A FAULTY BCM[BODY CONTROL MUDULE].BUT BEFORE WE ASSUME THISM CK ALL YOUR BATTERY CONNECTIONS MAKE SURE THEY ARE CLEAN..THERE ALSO COULD BE A WIRE IN THE DOOR THAT IS SEMI GROUNDING OUT CAUSING SUCH A DRAW ON THIS CIRCUIT..THIS MAY TAKE TIME TO DAIGNOSE AND YOU MAY NOT UNTILL SOMETHING SHORTS OUT AND THEN YOU CAN TRACE THE PROBLEM....I KNOW THE NEWS IS NOT WHAT YOU WANTED TO HEAR BUT SHORTS LIKE THIS CAN DRIVE YOU CRAZY !!!!IF MORE INFO COMES UP LET ME KNOW.. GOOD LUCK TO YOU,,TOM.