Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Does the engine reach normal operating temperature? Is coolant filled to proper level?
The different modes are vacuum controlled. (floor, dash vent, defrost) Check vacuum hoses in engine compartment. See if there is vacuum going to plastic reservoir located under battery mount tray.
With engine running and at operating temperature, feel both heater hoses. Are they both hot? Is one or both cooler than radiator hose?