SRS light could be a clue to having less than 10.1 volts. If alternator or voltage regulator are shot, that could give you an SRS MIL (but so will problems with the SRS system).
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.