Step 1 : Inspect track
Inspect the sliding door track for debris and to see if it's out of alignment. Use the crevice tool of a vacuum to suck up dirt in the track. Then carefully inspect the track for dents and bends. Straighten any bends or dents by hitting the track with a hammer backed up by a piece of wood.
If the sliding panel still doesn't move after cleaning and straightening the track, the rollers should be replaced.
Step 2 : Remove door
The sliding panel is supported on the track by two rollers located in its base. You will have to remove the door from the track to service them. If you are lucky and have the owner's manual for the patio door, follow the instructions for removing it.
Otherwise, open the door halfway and look for a hole in the end of the door at its base. It's on the latch side directly above the center rail of the track. Insert a screwdriver into the hole and turn it slowly until it engages the adjustment screw. Turn the screwdriver in a counter-clockwise direction to loosen the screw and raise the roller. As the roller goes up, the door will sink lower on the track.
Have someone hold the door upright while you loosen the roller screw at the other end of the door. With both rollers raised, the door rests on the bottom track. Then lift the door up and swing it out of the track. The door is heavy, so be careful and lay it flat on the floor.
Step 3 : Replace roller
The roller assembly is held in place by a screw located on the end of the door, just above the hole you put the screwdriver through or on the top edge of the door's bottom rail. Loosen the screw and the roller assembly will come out of the door.
Get a set of replacement rollers and reinstall them in the reverse order that your removed them. Make sure the adjusting screws are loose so the roller is in the retracted position when you put the door back in the track.
Step 4 : Replace door
Carefully lift the door to an upright position. Slide the top of the door into the upper track and swing the bottom of the door over the bottom track and lower it in place. Turn the adjusting screws clockwise with your screwdriver to raise the door off the track. This also pushes the top of the door into the upper track so that it can't fall out.
Adjust the rollers so the door glides easily on the track and the latch side of the door is parallel to the jamb.