I just bought a house that has a WeatherKing SCE/QCE/SFC 800 central air unit. Central air is pumped in to the first and third floor of the house (tri-level). We replaced our old thermostats (4) with new digital. 3 of the termostats only had two wires (only controlled heat) and are working fine.

The forth unit, located on the third floor had three wires, green-white-red. We installed a Honeywell RTH6300B digital thermostat in this room. To get the AC to work I had the green wire hooked up to G, the white wire hooked up to Y, and the red wire hooked up to Rc. When fall came, I tried to activate the heat on the thermostat but could not trigger anything. As a result, I have tried a multitude of different wire combinations and thermostat settings. Several times when I set the thermostat to "heat on" the out side unit will kick on and the fans will start blowing cold air.

At this point I am totally lost. Can I assume that this is only an AC unit and not also an electric heating supply. In others words, would it be possible for me to have both oil and electric heat in the house?

Any advice would be greatly appreciated.