Which vacuum lines go where on heater box on 89 chev van?

On an '89 Chevy van, the vacuum lines connected to the heater box typically include a line from the intake manifold to the heater control valve, which regulates coolant flow. Another line may run to the HVAC control panel to allow for proper temperature adjustments. Additionally, there may be lines connecting to the blend door actuator, which controls airflow between the heater and air conditioning. It's essential to consult a service manual for specific diagrams and configurations for your model.