need help with wiring on SW10DE water heater

I had to replace my water heater and did so with the exact model I had. however, the new unit is missing one wire. the old unit had 4 wires to hook up. the new one has only 3. the orange wire from the coach has nowhere to hook up and therefore the electric side will not work from the coach switch.
the old unit had blue, green, red, orange
the new unit has blue, green, red, no orange. the orange wire from my switch in the coach has no where to hook up. anyone know whats up?
it is the same unit. SW10DE suburban.