The driver’s side window in my Evolution Orange Miata started lowering to only about half way down and would it not go any further. However, it would roll back up without issue. Since the regulator motor still worked, I suspected the cable keepers for the power unit may be interfering with the mechanism some how.
When I installed the power regulator, the lower cable keeper had broken. I had to attach the lower cable to the door panel with a black cable tie to keep it in place.
So, I removed the door panel to inspect the cables. Sure enough the upper cable plastic keeper was broken allowing the cable to catch on the nylon guide at the bottom of the glass.
This kept the window glass from moving down past the cable and would only allow the window to lower half way down.
I used a black cable tie to attach the cable back to the inside of the door. The head of the tie is large enough to not go through the mounting hole, so the cable tie is just looped around the cable and back to the tie.
But my first attempt did not succeed. The old cable keeper held the cable out enough to catch the bottom of the glass again and the new cable tie broke when the window was lowered.
I moved the remnants of the old cable keeper away from the attachment point and installed another cable tie.
This time the cable stayed close to the inside of the door allowing full travel without interference with the window glass.
This is a very easy fix for a window that will only lower half way. It also only cost a few minutes of time and a cable tie. I love it when a plan comes together!