Why it happens:
* Worn-out parts: Over time, the internal parts of the lock mechanism wear down. The springs, levers, and linkages can weaken, break, or become misaligned, preventing the mechanism from returning to its correct position.
* Frozen mechanism: If moisture has gotten into the door, the mechanism could be frozen or stiff, particularly in cold weather.
* Physical obstruction: Something might be blocking the mechanism's movement (e.g., a piece of debris, a broken component).
* Binding: The linkage might be binding due to rust, wear, or misalignment.
Troubleshooting and Repair Attempts:
Before you take drastic measures, try these steps:
1. Lubrication: Try spraying a penetrating lubricant (like WD-40 or PB Blaster) into the lock mechanism through the keyhole or any visible access points. Let it sit for a few minutes to penetrate, then try working the lock mechanism gently with your fingers. Important: Avoid over-lubrication, as it can attract dirt and grime.
2. Manual manipulation: Carefully try to manipulate the interior door handle and the lock mechanism itself. Sometimes a gentle nudge in the right direction can dislodge a jammed component. Use a small, thin tool (like a flat-head screwdriver – but be very careful not to damage anything) if needed to carefully assist the movement of any visible jammed parts.
3. Check the exterior handle: Make sure the exterior door handle isn't stuck or binding. This can sometimes indirectly affect the interior mechanism.
4. Inspect the door panel: If you're comfortable removing the interior door panel (there are many online tutorials for this specific model year, search "1999 Chevy Tahoe door panel removal"), you can directly access the lock mechanism. This will allow for a closer examination and more targeted repair attempts.
If the above doesn't work:
* Professional repair: If you're not comfortable working on the door lock mechanism yourself, it's best to take your Tahoe to a qualified mechanic or locksmith. They have the tools and expertise to diagnose and repair the problem. They might need to replace the entire door lock actuator assembly.
* Replacement parts: You might need to replace the entire interior door handle assembly or the lock mechanism itself. Parts are available from auto parts stores or online retailers.
Important safety note: Be extremely careful when working with the door lock mechanism. Avoid using excessive force, as you could damage the mechanism further. If you're unsure about any step, it's always best to seek professional help.
