Here's a breakdown of the likely culprits and why:
* Blend Door Actuators: These small electric motors control the direction of airflow. They open and close doors to direct air to the dash vents, floor vents, defrost vents, etc. A failing actuator can cause the clicking noise (as the motor struggles) and prevent air from reaching certain vents. Since you're losing air from four dash vents, it's highly probable multiple actuators are failing or are already failed. The 2001 DTS is known for blend door actuator issues.
* Vacuum System (Less Likely): Older vehicles sometimes use a vacuum system to control airflow. A leak in the vacuum lines could cause similar symptoms. However, the clicking noise points more towards electrical components like the actuators.
* Low Refrigerant (Less Likely, but possible): While less probable given the specific symptoms, a severely low refrigerant charge *could* restrict airflow, but usually wouldn't cause the clicking.
Troubleshooting Steps:
1. Listen Carefully to the Clicking: Try turning the climate control to different settings (defrost, dash, floor). Does the clicking change location or intensity? This can help pinpoint which actuator(s) are failing.
2. Check Fuses: Before diving into repairs, check the fuses related to the HVAC system in your fuse box. A blown fuse could be a simple fix.
3. Professional Diagnosis: Given the complexity of the HVAC system, especially in a car of that age, a professional diagnosis is highly recommended. A mechanic with experience in Cadillac DTS models will have the tools and knowledge to diagnose the faulty actuator(s) and/or other potential issues effectively. Replacing these actuators often requires partial disassembly of the dashboard. Attempting this yourself could cause further damage if you're not experienced.
In short: The clicking noise and loss of air from multiple vents strongly point towards malfunctioning blend door actuators. Get a professional diagnosis to confirm and have the necessary repairs performed. Ignoring it could lead to further damage and potentially more expensive repairs later on.
