I am having some trouble with my CAC on my second story. We have two separate systems; one up, and one downstairs.

First: My system seems to run more than expexted, and more than the system downstairs, even at night. I beleive part of my problem is the thermostat location (upstairs hall, near return, near stairs, no ducts to hallway). For instance, if I set my thermostat to 74, the 4 bedroom will all reach about 71 degress before the system shuts down. This occurs even with the bedroom doors wide-open. I am guessing this happens because of the return sucking the warm-air from downstairs right past the thermostat? Should I move the thermostat?

Second: I have also noticed that even at times when the thermostat's room temperature equals that of the set temperature the system still runs. This eventually causes the thermostat to read a room temperature below that of the set temperature. For example: T-stat set @ 75, reads a room temp of 74 (in hallway) and the bedroooms are about 71 (seperate therometer). When this occurs the fan in the outside condensor unit is running. Any thoughts?

I am puzzled..Thanks for your help!