Bi-Level
When selecting the Bi-Level mode, air enters the module and passes through the evaporator core. Depending on temperature knob position some air may pass through the heater core. This air will then mix with the cooler air and then be discharged through the instrument panel and heater outlets.
Air flow design characteristics of the module will divert most of this tempered air out of the instrument panel outlets, with the air from the heater outlet being slightly warmer.