The Chargers will leave the fire and smoke behind this week when they take on the struggling Vikings at the Metrodome.  It’s been a streaky season for the Bolts, who have won three straight following last week’s 35-10 victory over the Houston Texans.  Antonio Cromartie scored two touchdowns on defense, and Philip Rivers threw for three more as the Chargers improved to 4-and-3.  It’s been a one-sided story on offense for the Vikings.  Minnesota comes in with the league’s second-best ground attack but ranks 30th in the passing game.  The Vikes have dropped two straight after losing at home, 23-16, to the Philadelphia Eagles.  None of the Vikings five losses this season have been by more than 10 points.  The Chargers won the last meeting between the clubs, 42-28, in San Diego.