Power Problems - Lenovo ThinkPad T420 User Manual

AC power adapter problems
• Problem: The ac power adapter is connected to the computer and the working electrical outlet, but the
power adapter (power plug) icon is not displayed in the task bar. Also the ac power indicator does
not light up.
Solution: Do as follows:
1. Make sure that the connection of the ac power adapter is correct. For connecting the ac power
adapter, see the Setup Instructions manual included in the shipping contents of your computer.
2. If the above step is correct, turn off the computer, then disconnect the ac power adapter and uninstall
the main battery.
3. Reinstall the battery and reconnect the ac power adapter, then turn on the computer.
4. If the power adapter icon still does not appear on the task bar and the ac power indicator does not
light up, have the ac power adapter and your computer serviced.
Note: If your computer is a Windows 7 model, to display the power adapter (power plug) icon, click
Show hidden icons in the task bar.

Power problems

Print these instructions now and keep it with your computer for reference later.
If your computer is getting no power at all, check the following items:
1. Verify the power switch. Refer to "System-status indicators" on page 11. The power switch is
illuminated whenever the computer is on.
2. Check all power connections. Remove any power strips and surge protectors to connect the ac power
adapter directly to the ac power outlet.
3. Inspect the ac power adapter. Check for any physical damage, and make sure that the power cable is
firmly attached to the adapter brick and the computer.
4. Verify the ac power source is working by attaching another device to the outlet.
5. Remove the computer from a ThinkPad Port Replicator Series 3, ThinkPad Mini Dock Series 3, ThinkPad
Mini Dock Plus Series 3, or ThinkPad Mini Dock Plus Series 3 (170 W). Refer to "Detaching a ThinkPad
Port Replicator Series 3, ThinkPad Mini Dock Series 3 or ThinkPad Mini Dock Plus Series 3" on page 164.
6. Remove all devices and then test for system power with minimal devices attached.
a. Disconnect the ac power adapter and all cables from the computer.
b. Close the computer display, and turn the computer over.
c. Remove the battery. Refer to "Replacing the battery" on page 111.
d. Remove the memory (SO-DIMM). Refer to "Replacing memory" on page 123.
e. Remove the PCI Express Mini Card. Refer to "Installing and replacing a PCI Express Mini Card for
wireless LAN/WiMAX connection" on page 130.
f. Remove the Ultrabay devices. Refer to "Replacing the device" on page 149.
g. Remove the hard disk drive and solid state drive. Refer to "Replacing the hard disk drive" on page
115 and "Replacing the solid state drive" on page 143.
h. Wait for 30 seconds, and then reinstall the SO-DIMM and the known good battery or the ac power
adapter to test the computer with minimal devices attached first.
i. Reinstall each device one at a time that you have removed in the earlier steps.
If your computer does not run on battery power, check the following items:
1. Remove and reseat the battery to make sure that it is properly connected. Refer to "Replacing the
battery" on page 111.
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User Guide