Summer 2010 vehicle started 'shutting down' on really hot days while driving, meaning it didn't stall but either the radio would go off for a couple seconds then come back on, or radio/tach/oodometer would all shut off briefly and idiot lights would come on, vehicle 'bucks' slightly like it completely lost power, then continues running! Had charging system tested, no problem, no codes registered. Dealer thought maybe battery, but tested fine. Dec 2010, didn't start oe morning, battery dead. Replaced and no problems at all last summer (2011). Now 1 month ago, problem starts again. Only happens on hottest days (AC on). Thinking it has to be heat related and electrical. If battery again, what could cause batter to only last 1.5 years? Appt. with dealer next Monday but afraid they won't have a clue again because no codes registered.