have a 2 story house with zone control. Downstairs cools a few degrees past what thermostat is set on while the upstairs cools about 10 degrees colder than set. This mainly occurs overnight. What might be the issue?
Zone dampers may be sticking partially open, or not closing at all. Also the dampers may be set to a min open position duct to under sized duct work. Check to se if your dampers are closing, and if they are set to a min open position.