AC/Heater Problem

[infiniti30]

I have a 99 I30 bought used earlier this year. It has the "automatic climate control" . When the temp is set on 65, the lowest setting, the AC is nice and cold, but if you put it up to 66 it is completely hot. In the winter, it did a similar thing with heat. If it was set on 85, the max temp, it would deliver lots of heat, but at 84 it was cold outside air.

Any ideas much appreciated.