When the red light is on the heater is heating and when it goes out the heater is off. After opening the door and loosing heat the light will stay on for awhile, but normally it should flash on and off maybe once or twice per second.
The top and bottom center vent holes on the newer models are a smaller diameter and don\'t get closed at all. Additional vents to the side of the center vents can be adjusted (top and bottom) and I only adjust them to maintain the desired humidity.
I believe the newer units also recommend the temp be set at 100.5 degrees.
I use an electronic thermometer/hygrometer in the center of the middle tray to initially set the temp and humidity. Take about 3 days without opening the door if you have the time to get these stable. After that use the eggs as your guide to determine if your temp should be increased or decreased knowing that some will hatch up to a day early, but most at 21 days.
There are a few other topics on this site on the subject that can be found by a \"search\". It may be worth the time.