Yes, a 1991 Buick Skylark 4-cylinder has a heater control sensor, though it might not be called that specifically in the repair manuals. It's more accurately described as a
coolant temperature sensor for the heater control system. This sensor monitors the engine coolant temperature and signals the control unit (usually a blend door actuator) to adjust the proportion of hot and cold air that mixes for the cabin heater. It's crucial for regulating the temperature of the air coming from the vents.
While not directly labeled a "heater control sensor" on parts diagrams, it's a vital component of the system's temperature regulation. You'll likely find it referenced as a coolant temperature sensor or a sensor related to the HVAC (Heating, Ventilation, and Air Conditioning) system.
