i would say it has more to do with the tractor being a 30 series, than anything else.  JD 30 series are cold blooded SOBs. i have a 4630 that will start when it gets pretty cold, as long as it is inside & plugged in, if it is one without the other it won't start.  has to be both.  that the only thing i don't like about mine, other than that....i think they are pretty solid machines.