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First you need to know which type you have. http://www.rainbird.com/landscape/products/sprayBodies/1800SAM_PRS.htm
This site will show pictures of the type of sprinkler you have. If you had the system installed this summer, I would call the installer. The adjustment should be free. For me, the easiest fix is to unscrew the head. Be very sure that no dirt gets into the pipe. Take the head to the hardware store and just replace it. The heads are inexpensive. Also be sure that dirt does not sit on the sprinkler head after watering. The 2 web sites should answer all of your questions.