I am trying to swap out a dual switch for a switch that has a dimmer for the ceiling fan light and a three position switch to control the fan. The original wiring had white to white on switch, black to black on switch, and one black from light connected to the top switch pole and the other black from the fan on the bottom switch pole. The new control doesn't specify what to do with the white. If I connect together the white to the other white wires at the receptacle, only the fan works, not the light. Can anyone help?

I actually figured it out. Basically, the white common connected to the appliance was being used as the return to the fan while the black in the same cable was being used as the return to the light. So, all I had to do was join the two other blacks (both hot) and hook those to the "service in" black wire on the switch unit. I don't know if it is standard practice to use the white common as a hot feed to a ceiling fan, but that's what appeared to be the case. Anyway, all is working correctly now.