One championship in 87 combined seasons and that one from 1963 when the Chargers were in the pre-merger AFL.
While their teams have made the playoffs with reasonable frequency, they normally melt-down, screw up, or otherwise stick a knife in the heart of their fans.
Add that to not one but two teams fleeing the city (NBA twice, Rockets and Clippers) and its a good thing the city has great weather.