Do I need to close the bottom to force the bees to find and get used to a top entrance? Used shims and left them 3/4 inch all across the top but not one bee has exited or entered that way yet? Still have bottom open.
They will find the top entrance, especially as you start adding supers and they have so far to go up.
Sometimes they use it and sometimes they do not. I have some that take right to it almost exclusively and others that refuse to use it at all no matter how tall the stack. Personally, I wouldn't try to force them to use it, let them do what they like. Worst hive I had would propolize it shut within a matter of days no matter how many I put in or where. Just think of it as extra ventilation if they ignore it.
I am concerned that it will be to much ventilation if I leave the bottom entrance open it will work like a smoke stack and suck all the heat out?
Your current bees are used to using the bottom entrance. As new bees hatch and they find the upper entrance, they will start using the upper one. As more bees hatch, the more the upper entrance will used. I would venture to say, that 90% of my bees use the upper entrance, even as crowded as it can get, and 10% use the lower. Even in the spring, as the brood has moved up, they will use the upper entrance to do their cleansing flights.
Here is a video I took of an experiment I did. I had my entrances reduced with a board. I just slid the board over to put the entrance on the other side. For the longest time (21 days probably) they landed at the old entrance and then would march across the reducer to the new entrance. It was amazing to see how close they would come to the old entrance every time. Great internal GPS!
Jay
Video (http://www.youtube.com/watch?v=1N75CQqyQEY#)