I have the same problem with my regulators . Everyone I know that owns a 929 have the same issue. The problem is the wire in the regulator that pulls the windows up and down, after a while it will get tangled on the regulator motor. I took my regulators out and they all had the same problem, the motor works but the wire is all tangled up.Once this happens all you can do is get new ones. I got mines on Ebay $49.95 for the front passenger and $77.95 for front drivers side. I don't the the price for the rear. If you still need diagrams of how to remove the door panel and regulator just let me know and I'll post some PICS.