It sounds like you burned the belt. Turn the unit over, remove the cover plate where you see the brushes. On the side of the brush roller is where the belt is located. The belt should be very tight on the roller. Also, you may see little black rubber pieces stuck to the area where the end of the roller is or in the part where the belt runs. Get your owners manual out and read how to change the belt. I'll bet when you ran over the carpet it hung on some of the nap and hung the brush roller up for a second or so. That's all it takes sometimes to fry the belt on some vacumes. Sometimes new vacumes come with a new belt. Look in the bag or box and install it.