If the glass goes down you know the motor and everything else electrical is okay. If it goes up smoothly if you help it, the first suspect is gummed-up rubber channels. Spray them liberally with Silicone Spray Lube. That goes on like water, evaporates, and leaves a film of "slippery" behind. Also check the cables and pulleys. A frayed cable may only go one way freely. A cracked pulley will let the window move unevenly and it can bind.