First stop the day time napping Ihe may not need it now,,It is a habit he has got into to so the habit needs to be broken, maybe he isnt tired enough does he get plenty of daytime games and stimulation. Its tough but by going in to him in the night you are enabling the behavior, you may have to let him call for you, just call back its okay go back to sleep, if you go in he knows thats what will happen, ,but if you stick it out he will get fed up when it isnt working. There is a book out there called SOS Help for Parents ' by Lynn Clark, you may find some help there. Good Luck