2000 jimmy heater problem

just replaced heater core in 2000 jimmy. heater does not work still. coolant is flowing through the core. on the passenger side near the kick panel there is a wire plug with 3 wires (black, brown, blue)- which are the same color (and number of) wires as on the rear of the a/c temperature controller. i think this is my problem. does anyone know where this plug plugs into? i have looked and can't see.