yeah i cant remember what the bits are called but if you look at the sides from inside the car under the plastic thing you will see a silver metal thing. thats the bit that the motor moves back and forth that opens and closes the sunroof. you can see if they both work by making the sunroof slide back they when you try to close it again only one will move back again and the sunroof with jam. then you have to wind it back with allen key.
if only one moves back then the other side is broken and you need a new sunroof.