An awesome team of students from our education program made this wiki.
Display won't turn on
You keep trying and trying but your Thunderbolt Display just refuses to turn on.
No video/signal from the display
Try to update the firmware for the display to make sure you have completely updated your computer. Restart the computer and unplug; then plug back in your monitor. If this does not fix the problem, try and plug the display straight into the wall, as a surge protector could also be the problem!
Black screen after plugging in to laptop
Before going through with taking your display apart, first double check to make sure that all cords are attached and that your display is plugged into an outlet.
Double check that all connections are plugged in and secure. Try unplugging and plugging back in the video adapter or cable. If the problem persists, try using another adapter to see if it works.
Display won't wake up after waking up computer
No audio or distorted audio
Your display is working fine but you cannot get any audio output from it.
No sound coming out of display
The main problem is most likely coming from your connected computer. Take the thunderbolt cable and unplug it from your connected computer. Wait a few seconds and then plug the cable back in. If the problem continues, try restarting your computer.
Audio becomes distorted after using speakers for an amount of time
If not done so already, update your computer to the latest software. Next, try using your thunderbolt display without having any usb devices plugged into it. If the problem still persists, you may need to inquire Apple about this issue, replace the speakers in the display, or use external speakers.
Usb ports stopped working
The thunderbolt display will not recognize any usb devices connected to it
Usb ports stop working after waking up connected Macbook
Update your Mac to the latest software and test to see if the problem persists. If it does, whenever you close your Mac (put it to sleep), unplug the video adapter that connects your Mac to your display. Also, try resetting the SMC on your Mac.
Faulty usb ports
Your USB ports on your display may be faulty and may need to be replaced.
Scrambled Display, No Display, intermittent display
When the Thunderbolt display is attached to the host Mac, display is distorted, or non existent. Unplugging and replugging the display gives varying results
It is very possible that the cable has become crimped, cut, worn, or the display connector is damaged or defective. Evaluate the condition of the attached cable and connector.
1) Disconnect the Thunderbolt display cable from the host computer. Leave it aside.
2) Connect a known good Thunderbolt peripheral cable (male-male) to the Thunderbolt port on the back bottom edge of the display (next to the FireWire 800 and USB 2 ports). Connect the other end to the host computer. Power on both the Thunderbolt Display and host computer.
3) if the display acts as expected (shows a good solid display), replace the thunderbolt cable that is attached to the back of the display.