* Weak Motor: The most likely culprit. The motor is struggling to overcome friction in the window regulator system. The clicking is the motor engaging and disengaging, but not having enough power to consistently lift the window. This worsens over time as the motor brushes wear.
* Window Regulator Problems: The regulator is the mechanism that moves the window. Problems here include:
* Broken or binding regulator: The plastic components of the regulator can crack or break, especially the plastic clips and gears. This can cause binding and prevent smooth operation, making the motor struggle.
* Seized or stiff window tracks: Dirt, grime, and old lubricant can cause the window to bind in its tracks. This adds significant friction and loads on the motor.
* Bent or damaged window: A bent or warped window can bind in the regulator and tracks, putting extra strain on the motor.
* Wiring and Connections: While less likely if it works *sometimes*, a problem with the wiring harness, switch, or connector could intermittently interrupt power to the motor. Corrosion or loose connections are the most common causes. Check the switch, the connections at the door, and the harness that goes to the window motor itself.
* Power Supply Issues: This is less probable given the intermittent functionality, but a weak battery, faulty fuse, or bad wiring in the main power circuit *could* be contributing factors. Check the fuse related to the power windows.
* Window Switch: While the switch may feel fine, an internal problem within it could be causing intermittent failure. Try testing with another window switch (if possible), to rule this out.
Troubleshooting Steps:
1. Check the Fuse: Locate the window fuse and ensure it's not blown.
2. Inspect the Window Tracks: Clean and lubricate the window tracks. Check for any obstructions.
3. Listen Carefully: When the window is sticking, try listening carefully to where the binding sound is coming from. This helps isolate the problem (motor, regulator, or track).
4. Manually Operate the Window (Caution!): If you can access the window regulator mechanism (often requires removing the door panel), try carefully moving the window up and down manually to check for binding. Be very careful not to pinch your fingers or damage other parts of the system!
5. Test the Motor (advanced): If you have a multimeter and some electrical knowledge, you can test the motor itself to see if it is drawing the correct current.
6. Visual Inspection of Regulator and Motor: Accessing the regulator and motor usually means removing the door panel. Once you have access, visually check for any obvious damage to the parts.
If you're uncomfortable with any of these steps, it's best to take the vehicle to a mechanic experienced with auto electrics or window repair. Replacing a window regulator is often a fairly involved job.
