Led Ceiling Fan Install Ceiling Fan On Old Light Box?

Install Ceiling fan on old light box? - led ceiling fan

I helped my brother install a ceiling fan. I know that some power lines and their homes.
It was a fan before, but had no light, and I think a lot of balance. When we were hanging from the fan, which will begin to move in any direction, and swings back and forth before they block the fan's heart instead. This leads us to believe that the light field is not that great is connected (the house) is almost 30 years old.
I guess its one of those light boxes that are connected to a rod, it feels like when installed in each timber.
What can we do to ensure the best body?