pulsating lights

hello all,i have a 2002 trailblazer with the headlights pulsating with the idle including when idled up they pulse faster....any ideas?

Check alternator output when it does this. Do the interior lites also pulse?

does it all the time but have not checked to see if interior lights flicker as well,i will check that out and post.as for checking alt plug u mean to see if i am getting that same pulse thru the electric?

See if the alt output also fluctuates.