It is really common for cheesecakes to crack on top, and this is usually due to temperature changing too rapidly. First, check that your oven is cooking at the temperature you're setting it for with an oven thermometer. Make sure it's not too hot. Next, let the cheesecake cool slowly by leaving it in the oven, turning the heat off, and cracking the door open for 30 minutes to 1 hour. This lets the oven temperature reduce slowly instead of the rapid change.  Last, it may be a moisture issue. Depending on the climate and altitude you live at, you may need to place your cheesecake in a water bath during the baking process to prevent cracks.