1. Check the Blend Door Actuator: This is the most common culprit for clicking noises in that area. The blend door actuator controls the flow of air between the vents and the defrost. A failing actuator can cause clicking as it struggles to move the blend door.
* How to check: You'll likely need to access it by removing parts of the dashboard. This requires patience and potentially some specialized tools. Consult a repair manual for your specific year and model Silverado to determine the exact location and removal process. Once accessed, you can try manually moving the blend door to see if it's stiff or binding. A clicking sound when you manually operate it strongly suggests a bad actuator.
* How to fix: Replace the blend door actuator. These are relatively inexpensive and readily available online or at auto parts stores.
2. Relay Clicking: A relay located under the dash could be clicking due to a malfunction or a short circuit. These are small electrical switches that control various components.
* How to check: Again, you'll need to access the area under the dash. Locate the relays (they're usually small square or rectangular boxes) and listen carefully as you turn various functions on (like the blower motor, headlights, etc.). If you can pinpoint a relay that clicks excessively or erratically, it may need replacement.
* How to fix: Replace the faulty relay. It's important to identify the correct relay before replacement. Your owner's manual or a wiring diagram may be helpful.
3. Wiring Harness Issue: A frayed or loose wire in the harness running under the dashboard could be causing the clicking as wires rub against each other or a metal component.
* How to check: Visually inspect the wiring harness in the area. Look for any signs of damage, chafing, or loose connections. This will require some disassembly of the dash.
* How to fix: Repair or replace any damaged wiring. This may require soldering skills or a trip to a professional.
4. Other Possibilities (Less Likely):
* Clock spring: If the clicking is related to steering wheel functions (airbag, cruise control), the clock spring might be the issue.
* Other actuators: Similar to the blend door actuator, other actuators (e.g., for seat controls) could be making the clicking noise.
* Loose parts: Something loose under the dash could be rattling and making a clicking sound.
Important Considerations:
* Safety First: Disconnect the negative battery terminal before starting any work under the dashboard to prevent electrical shocks.
* Repair Manual: A repair manual specific to your 1993 Chevy Silverado is invaluable. It will show you where components are located and how to remove them safely.
* Professional Help: If you're not comfortable working on your vehicle's electrical system, it's best to take it to a qualified mechanic. Incorrectly diagnosing or repairing electrical issues can lead to further damage.
Start with the blend door actuator – it's the most common cause of this type of clicking noise. If that's not the problem, systematically investigate the other possibilities. Remember to take your time, be methodical, and prioritize safety.
