mussac240

Hi i got a 2001 c240 se 2.6L and iv been having a dead battery issue but i took the car to autozone and farm n fleet three time and had the batt and alt tested and both where good i even took the batt out and took it to autozone they charged it and said its fine but when i brought it home and checked it it was at 12.06 but it kept falling it still started car i then took it back to autozone they said batt and alt are fine that time to then today after charging all night i went to the gas station and went for about a half hour came out and wont start i have the sunroof switch dissconected because the small fan inside the unit wont stop running and when i use a test light it shows power in some of the fuses in the engine and some fuses in the trunk when the car is turned off i was gona get a icarsoft i980 but will that tell me if i have a short or would a carsoft multiplexer 7.4 be better not sure what to do thanks for all your help