We own a 90 or so year old house that has been extensively renovated. Since the renovation and rewiring, every time we turn on the ceiling fan, there are sparks at the switch and the lamp plugged into an outlet related to that switch also flashes on and off. The switch does not have a switch plate on it because none fits. It's too late to go back to the original contractor who has left the State. Several handymen have claimed to fix it, or that it isn't really anything to be concerned about. Is this dangerous? Is there a fix for this that doesn't involve going into the walls and rewiring?

Thanks