Whats going on guys,

All my lights dim like crazy when i start my truck for about 2 seconds or so ? and then go back to bright ??is this my Alternator ??

I know all cars dim a little but it even does it when i go to roll the windows down while drive ing

Let me know what you guys think

 

That would be the battery. It'll be the alternator only if it isn't charging the battery properly.

 

AutoZone, AdvanceAuto, most auto part stores can do a free load test on your battery to confirm it's bad.