1. Identify the Problem:
* No air from vents: This could be a blend door problem (controlling hot/cold), a clogged filter, or the fresh air door. Rule out the other possibilities first.
* Only recirculated air: This strongly suggests a problem with the fresh air door or its actuator.
* Intermittent fresh air: This points to a linkage or actuator problem.
* Loud noises from the dash: A broken or binding door or linkage might be making noise.
2. Accessing the Fresh Air Door:
This is the most challenging part. You likely need to remove parts of the dashboard to access the blend and fresh air doors. This is a complex job, and requires significant mechanical aptitude. Consult a repair manual specific to your 1999 Chevy Suburban. These manuals (available online or at auto parts stores) show detailed diagrams and steps. Improper removal can cause damage.
General steps (will vary depending on the specific model and problem):
* Disconnect the battery: Safety first!
* Remove the glove box: This often provides some access to the area.
* Remove the radio and other dash components: Be careful to disconnect electrical connectors before removing anything.
* Locate the HVAC assembly: This is the housing containing the blend doors and fresh air door.
* Inspect the linkages and the fresh air door itself: Look for broken parts, loose connections, or obstructions.
3. Possible Fixes:
* Lubricate the linkages: A simple fix if the door is sticking due to dried lubricant. Use a silicone-based lubricant.
* Replace the linkage: If the linkage is broken or severely worn, it needs replacing.
* Replace the actuator: The actuator is the motor that moves the fresh air door. It might be faulty and needs replacement.
* Replace the fresh air door: In case of a damaged door, you may need a replacement. This requires considerable disassembly and reassembly of the HVAC assembly.
4. Tools You Might Need:
* Repair manual specific to your 1999 Chevy Suburban
* Screwdrivers (various sizes and types, including Phillips and flathead)
* Socket wrench set
* Pliers
* Silicone-based lubricant
* Replacement parts (linkages, actuator, door)
Important Considerations:
* Complexity: Accessing and repairing the fresh air door is a complex job, often requiring significant mechanical skill.
* Professional Help: If you're not comfortable working on your vehicle's interior, take it to a qualified mechanic. Improper repair can cause further damage.
* Repair Manual: A repair manual is crucial for this repair. It provides detailed instructions and diagrams.
In short, this is not a simple DIY project. Without a repair manual tailored to your specific vehicle and year, it's very likely you'll cause more damage than good attempting this repair. Start with the repair manual, and if you lack experience, consider professional help.
