Outer Limits 4x4 Board

Hi everyone,
I got my first sierra about 3 days ago, and it is great. There is only one problem, at first the revs dropped and the engine stalled when it was cold, so i adjusted the fast idle and it fixed that problem.
Except now at idle if i switch the lights or the heater on it revs up to about 2000-2500 rpm from idling. Has anyone come across this problem or is this a normal sierra thing?
Thanks for your help,
Joe

it is intentional, but shouldnt go that high =) usually turning the lights on drops you around 100-200rpm, so it ups the idle with lights to counter that power draw.