| The Problem is caused by the seal inside the door panel usually caused in the summer and you will notice a streek mark on the window. Check this before taking to the garage as they will alsways tell you that you need a new motor.
First check to see if you can hear the motor click when you try to make the wondow go down. If this is there then the motor is fine! If not you may have either a loose connection (this is another common problem) or a dead motor.
If the motor does click you have 2 options. the first is banging the door panel just above the speaker (this may not always work but 50% of the time it will)
The 2nd option to try is taking the door panel off and replacing the new seal inside. Then if this fdoesn't work consult your local dealer | 
