I am trying to install a Honeywell RTH7500D Thermostat without success. When I install it, I have no access to Emer. (AUX) heat and the fan will not turn on. The original configuration is as follows:

Blue - Y2
White - W
Yellow - Y1
Green - G
Red - R
Black - C
Orange - O

Could someone give me the correct configuration for the wiring? Thanks.