Why is the screen not working properly?

So I was repairing my phone and changing the screen when the new one didn't work. Or so I thought. In certain angles, more whens its in sunlight, you can very dimly see the screen. Now the brightness is all the way up but it still has the same problem. I put the old screen back on it and it stopped working the way it did. (the old one was fine just has cracks) Now when I put the connectors together I did feel a slight hotness. Does this mean the connection was short circuited? Like I said, the screen works, but doesn't. Same problem when I kept putting new screens on it. Any suggestions or answers? Thanks