Forum discussion tagged with T420.
  1. R

    Lenovo T420 issues with replacement battery

    Bought a 3rd party replacement battery for my Lenovo T420. Powered down, removed AC adapter, installed the new battery, plugged AC adapter back in, powered up. Waited 10 minutes, unplugged AC adapter, PC shut down. Plugged adapter back in, powered PC back up, left up for 10 hours to ensure full...
  2. W

    How to get Lenovo T420 to turn back on without the battery?

    I used webworkings instructions on how to turn on my T420 ThinkPad to see if it needs a new battery. It does need a new battery, but I then unplugged my laptop and followed the instructions again because it was back to being dead. This time I can't get my laptop to turn on without the battery...
  3. B

    Windows won't Automatically switch from speakers to headphones and vice versa.

    I updated my windows 7 pro thinkpad t420 to windows 10 pro. Normally when you connect your headphones, it should switch to it for playback, but what i have to do is switch it as default device. Vice-Versa as well, once I have my headphones connected and its set as the default device then I...