i have a john deere 240 that's been working/starting fine, until now. went to use it and it just clicked when turning the key. first thought, battery. i test it, says battery is good. i jump it and it starts right up. use it a little bit, turn it off,starts right up. next day, same thing. so, i buy a new battery anyway. put it in, starts fine. next day same thing. battery is up full, not drained, barely move under load test. i hear the click left side , behind operator. again starts fine with a jump. advice please.