I bought the vehicle new and it never seemed to really blow hard from the vents, even with max AC and recirculation selected. This past several months it would often not blow at all or blow based upon the engine RPM. The local dealership is saying that is was due to a bad battery. I am having a hard time following that line of thought because as I understand it once the engine is running the alternator should be handling all of the electrical load. Am I missing something?