The Chargers (3-4) dropped their third straight. San Diego had a final chance, but quarterback Philip Rivers' pass was batted away by Browns cornerback Buster Skrine with 1:24 left.
Rivers finished 18 of 34 for 154 yards but had a potential touchdown pass dropped by Robert Meachem in the third quarter.
With winds off Lake Erie gusting to more than 40 mph and a steady rain falling from the opening kick to the final whistle, neither offense could get anything going.
So the Browns turned to Richardson, their young star who had been limited in practice all week with a rib injury he sustained two weeks ago in a win over Cincinnati. But unlike last week when he was tentative hitting the hole, Richardson ran with purpose from the outset. He also had an important 12-yard reception in the fourth quarter when the Browns were backed up near their goal line.
Because of the bad weather, the Chargers, too, were forced to go to the ground and Ryan Mathews picked up 95 yards on 24 attempts.
Nick Novak kicked field goals of 43 and 31 yards for San Diego, which blew second-half leads in consecutive losses to New Orleans and Denver before its bye. But the Chargers never got ahead in this one and Meachem's huge drop will be the play that haunts coach Norv Turner this week.
Richardson's TD run gave the Browns a 7-0 lead in the first quarter.
Two plays after quarterback Brandon Weeden converted on a 4th-and-1 with a sneak to keep the drive alive, Richardson took a handoff up the middle, broke two tackles and was kept upright by right guard Shawn Lauvao, who wrapped his hands around his teammate, before scampering into the end zone for his fifth TD.
The Browns were effective getting Richardson outside with quick pitches, plays that allowed him to minimize smacked in the ribs and forced some of the Chargers defensive backs into situations where they had to try to bring down the bruising back in space not an easy job.
San Diego's offense sputtered for much of the first half but Rivers moved the Chargers in the final two minutes, setting up Novak's 43-yard field goal as time expired that cut Cleveland's lead to 7-3.
The Chargers missed a chance to take the lead midway through the third when Meachem failed to hang on to what would have been an easy TD pass. Meachem got behind Cleveland's secondary and was wide open at about the 25-yard line when he let Rivers' toss slip through his hands.
Novak's 31-yard field goal brought the Chargers within 7-6 in the third.
Following Richardson's TD, the Browns punted on eight consecutive possessions and were in trouble backed up at their own 7. On second down, Weeden's pass was tipped at the line and nearly picked off by safety Atari Bigby. Given new life, Weeden then hit Richardson on a swing pass for a critical first down and the Browns were able to run off some time before Rivers got the ball back with 2:36 left.
But San Diego only got as far as Cleveland's 44 and Rivers threw four straight incompletions to end a frustrating day.
San Diego 6, Cleveland 7
San Diego 0 3 3 0 6
Cleveland 7 0 0 0 7
Cle • Richardson 26 run (Dawson kick), 4:17.
SD • FG Novak 43, :00.
SD • FG Novak 31, 2:33.
Attendance • 65,337.
First downs 17 15
Total Net Yards 265 250
Rushes-yards 34-117 33-133
Passing 148 117
Punt Returns 5-46 2-7
Kickoff Returns 2-32 2-47
Interceptions Ret. 0-0 0-0
Comp-Att-Int 18-34-0 11-27-0
Sacked-Yards Lost 1-6 2-12
Punts 6-46.5 9-39.6
Fumbles-Lost 2-1 2-0
Penalties-yards 3-15 4-35
Time of Possession 30:52 29:08
Rushing • San Diego, Mathews 24-95, Brown 4-17, Battle 3-6, McClain 2-5, Meachem 1-(minus 6). Cleveland, Richardson 24-122, Weeden 4-4, Ogbonnaya 1-4, Hardesty 3-3, Cribbs 1-0.
Passing • San Diego, Rivers 18-34-0-154. Cleveland, Weeden 11-27-0-129.
Receiving • San Diego, Brown 7-85, Floyd 4-43, Gates 2-14, Rosario 2-11, Mathews 2-9, Clary 1-(minus 8). Cleveland, Gordon 3-46, Little 2-28, Watson 1-14, Cameron 1-12, Richardson 1-12, Ogbonnaya 1-9, Cribbs 1-7, Smith 1-1.
Missed Field Goals • None.