Use a multi-meter to make sure that the motor is getting the correct voltage. Attach the probes of your multi-meter to the motor’s plug and toggle the switch up and down. Make note of the voltage in both directions. Your owner’s manual should list the specific voltage required. Ensure that the window moves freely during this test. There should be no slow spots or blockages. Unplug the motor. If you the motor is getting the proper voltage but not functioning properly, you likely need to replace it. Start by unplugging the wiring connectors from the motor.
From the first steam powered coaches to today's super-cars, an automobile is a vehicle that undergoes constant changes and improvements. The first cars that were invented could barely replace the horse, were not reliable and didn't show any promising future. But people who were visionaries kept the idea alive, pressured forward thus making the car a irreplaceable part of our lives.
If the battery light is on and you're still driving the car, turn off as many electrical accessories as you can, such as the stereo, air conditioning or heater, and avoid using electrical controls such as power windows. Reducing the amount of electricity the car is consuming will increase the distance you can drive before the battery is discharged. Get to a mechanic as quickly as possible, and have the battery, wires and charging system checked out to find the cause of your problem and what you need to repair or replace.
If belt tension is correct, then the next item to check is the alternator itself. You now have two choices - you can test the alternator yourself with a simple test using a voltmeter, or you can have the test performed by a professional. If you choose to do the test yourself, then you will need a DC voltmeter, or a multimeter. Such a unit can be purchased at most auto supply stores, hardware stores, department stores, home improvement stores, etc.