The battery charges only when the laptop turned off. The battery charge LED lights up as normal and the battery gets charged to 100% while the laptop is off.
When the laptop is turned on, the battery charge LED goes off even if the adapter is still plugged in.
1. AC power adapter failure.
2. Battery failure.
3. Broken/loose power jack.
4. Motherboard failure.
Possible troubleshooting steps and repair solution:
1. This problem could be related to a faulty AC power adapter. It's possible that the AC adapter doesn't provide enough power when plugged into the laptop. To find out if this is your problem, you'll have to test the laptop with another working adapter.Replace the adapter if needed.http://www.chargerbuy.com/replacement-acer-aspire-9400-ac-adapter-19v-3-42a.html
2. There is a slight chance that you have bad battery. Test the laptop with a know good battery and replace the faulty one if needed.
3. The battery charge problem could be related to the power jack. Maybe the jack is broken or not making good contact with the motherboard. It is necessary to remove the motherboard and take a closer look at the power jack. Resolder or replace the jack if needed.
4. If the power jack is in a good working shape and new power adapter with battery do not fix the problem, most likely you have a faulty motherboard. Replace the motherboard if needed.