Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP
What you describe sounds like a faulty blend door actuator. The noise you are hearing is the actuator skipping because the gears are worn out. Can you tell whether the heater and AC are working normally? Does it switch from vent to floor to face like it should?
Does it seem like the re-circulation setting is working?
Ok. Well we need to figure out which actuator is malfunctioning. If you switch the vent position or switch from re-circ to normal, or switch from heat to AC does the noise change?