We moved into our house in Nov-2007. I just turned the central air system breaker switch back to the on position for the summer and I noticed that whenever the heat comes on (Haven't even flicked the switch over to cool yet on the thermostat), the central air unit is also now operating outside. Also the same effect when I turn on the ventilation system. Seems a bit unusual to me. It's a 3 tone Carrier unit (Puron) 13 seer.