Temperature Lever/Dial
WARNING: This page does not describe the selected car, but rather 38 other vehicles, including the 1987 Pontiac Sunbird, 1987 Pontiac Safari, 1987 Pontiac Grand Prix, 1987 Pontiac Grand Am, and 1987 Pontiac Firebird. However, it is still accessible from the selected car via links, so may be relevant.
When temperature lever/dial is placed in "COLD" or "C" position, no airflow is allowed through the heater core. If the lever is placed in "HOT" or "H" position, all air flows through the heater core.