* Broken or worn regulator: This is the most common cause. The regulator is the mechanism that moves the window up and down. Over time, the gears can strip, the motor can fail, or the cables can break. A partially broken regulator might allow the window to go down some before the damage prevents further movement.
* Binding in the window track: Dirt, debris, or corrosion can build up in the window tracks, causing the window to bind and stop halfway.
* Faulty window motor: While less common than a regulator issue, a weak or failing window motor might have enough power to lower the window partially but not completely.
* Electrical problem: A short circuit, blown fuse (check your owner's manual for the window fuse location), or problem with the window switch itself could prevent the window from fully lowering. This is less likely if the window *partially* works.
* Stuck window latch: A problem with the window latch mechanism might be preventing full lowering.
Troubleshooting Steps:
1. Check the fuse: This is the easiest and quickest check. Replace it if blown.
2. Inspect the window tracks: Carefully look for debris or obstructions in the tracks. Clean them with a brush and compressed air if necessary. Lubricate the tracks with silicone spray (avoid WD-40 as it can attract dirt).
3. Listen for unusual sounds: When you try to operate the window, listen carefully. Grinding, clicking, or whining sounds often indicate a problem with the regulator or motor.
4. Manually try to move the window: With the window halfway down, carefully try to gently push or pull the window up and down. If it moves freely by hand, the issue is likely with the regulator or motor. If it's very difficult to move, the track is likely the culprit.
5. Inspect the regulator (if accessible): You may be able to access the regulator by removing the door panel. This requires some mechanical skill. Look for obvious signs of damage like broken cables or stripped gears. This is the most likely diagnosis given your description.
If you're not comfortable performing these checks yourself, it's best to take your Suburban to a mechanic. Repairing a window regulator often involves replacing the entire mechanism which can be moderately expensive.
