The fabric of a roller shade is attached to a hollow cylinder mounted at the top of a window. The shade can be adjusted to cover as much of the window as desired. Inside the cylindrical roller is a spring. When a cord is pulled to lower the shade, the spring uncoils. A flat pin catches in a ratchet at one end of the roller to hold the shade in place. When the cord is jerked, the ratchet releases and the spring coils up, turning the roller to raise the shade. Troublesome roller shades are easily adjusted to glide up and down as required.
Push the roller cylinder up against the top of the top of the window surrounding it to free it from the brackets that hold it. Lift the cylinder out of the brackets. Roll up the fabric of the shade manually.
Keep the roll tight, neat and tidy, with no stray edges sticking out at either end of the cylinder.
Lift the roller back into its brackets. Then pull the shade down halfway. This will put some tension on the spring, which has become too loose to turn the roller.
Remove the shade from its brackets a second time and roll it up tightly by hand once more. Replace the shade again. Pull the shade fully down, then jerk the cord to raise the shade in the normal way. Often, simply removing and replacing the shade in this way is enough to return tension to an overextended spring, allowing the shade to function normally. If there is no improvement, remove the shade from its brackets a third time.
Unroll half the shade fabric by hand while the roller is still out of its brackets.
Grip the flat pin at the ratchet-end of the shade firmly in the jaws of a pair of pliers.
Twist the pin in a clockwise direction until you feel the spring inside the roller begin to tense up, then pull. Allow the pin to slip back counterclockwise a little, until the ratchet engages. You have now tightened a roller spring that had become completely extended and was too slack to do the work required.
Lift the roller back into its brackets and pull the cord to raise the shade. It should now raise and lower as desired.
You may need to repeat the steps several times to get as much tension on the spring as you require.