How do i adjust the headlights on my chevy van

SOURCE: 2005 chevy express van where is Headlight adjustments

here is a link to a repair guide for your vehice that will help you with the headlights along with any other thing you might need.
http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152800b4a31

SOURCE: 2005 Chevy express van, How do I adjust the

The adjustment screws/nuts should be located either on the top of the headlamp assembly, behind the headlamp assembly, or near the frame rail by the radiator support.

You will have vertical adjustment screws for each independent beam (separate highs and separate lows, but will be same screw if highs and lows are the same bulb). You may also have additional horizontal adjustment screws as well

Park your car on a level ground 30 feet from a wall and measure the height from the ground to the bulb and mark on a wall (do this for highs beams and low beams if the bulbs are separate, if highs and lows are the same bulb, only do it for the lows)

If the headlights read VOR, then aim the brightest part or cutoff part just below the mark on the wall. If it says VOL or nothing, aim them 2 inches below the mark on the wall.

SOURCE: My 2005 Chevy Van front headlights just won't go

If the ground wires from the headlamps are securely tight without any corrosion I suggest the headlamp switch in you van is at fault