Electric Window Problem

Evening all,

My motor gave up on my driver's side window, so I bought a new motor, tested it and fitted it and put everything back together (a little prematurely!). When I tried the window, it got to about 2 inches from the bottom, clunked as if it was catching on something and then went into the door as normal. When I pressed the switch to close it, it struggled on whatever it was caught on, clunked and then went back up as normal. Does anyone have any idea what it might be getting caught on? Everything is in the right place and tightened up, so I'm a bit puzzled.

Thanks,
Charlie.

For want of a better suggestion, check the nylon wheels on the mechanism. I found bits missing out of several of mine when I had trouble winding up and down.