When I plug the charger in the laptop, the power is reaching the battery pins, but it doesn't charge the battery (I checked it with Voltmeter, there was 3 or 4 Volts on the pins). If the battery is not charged up and the charger is plugged, the laptop doesn't switch on . If I take of the battery and leave the charger plugged, it is not able to turn on also. The battery light lights only when the battery is charged up and the laptop is turned on. If the charger is plugged in and laptop is switched off and battery is in, there is no sign of charging (no light on). Can someone help me with this problem? Is it the mother board? Or is it anything else what is able to repair. Thanks in advance.

Check the connector where the charger plugs in. See if you can wiggle the pins. If they feel loose, then it has broken loose from the motherboard. If that's the problem, it might be fixed by resoldering.