| Key | |||
| 1 | LED #1 | 5 | LED #5 |
| 2 | LED #2 | 6 | LED #6 (Only present in Quad processor models) |
| 3 | LED #3 | 7 | LED #7 |
| 4 | LED #4 | 8 | Edge of logic board |
| 9 | Top bank of DIMM slots | ||
Normally, all LEDs should be off. When you remove the air deflector shield, the third, fourth, and fifth LEDs may turn on. If they're still on when you replace the air deflector shield, remove and then reposition the shield.
Note: LED 7 will momentarily flash when the power button is pressed during start up. This is normal behavior.
Here's a look at what LED light statuses you should pay attention to, and what you should do if you see them:
| LED number | Color | What to do |
| 1 | Red | Contact Apple or an Apple Authorized Service Provider |
| 2 | Red | Contact Apple or an Apple Authorized Service Provider |
| 3 | Red | The air deflector shield is not in place or not closed properly. Reseat the air deflector. |
| 4 | Yellow | The air deflector shield is not in place or not closed properly. Reseat the air deflector. |
| 5 | Green | The air deflector shield is not in place or not closed properly. Reseat the air deflector. |
| 6 (Quad models only) | Red | Contact Apple or an Apple Authorized Service Provider |
| 7 | Red | Contact Apple or an Apple Authorized Service Provider |
(If you're checking out your logic board, you may notice two other LEDs—one to the right of the top bank of DIMMs, and one near the bottom edge. These two LEDs were only used in manufacturing, and you can safely ignore them.)
In addition to the LEDs on the logic board, the power light LED on the front of the computer can offer additional diagnostic information:
| Key | |
| 1 | Front panel LED |
Here are the power light's various statuses and what this LED is telling you:
| Power light status | What it means |
| On and solid | Computer is on and running |
| 2 flashes, pause | No memory (RAM) is installed |
| 3 flashes, pause | Incompatible memory (RAM) is installed |
| 4 flashes, pause | No good DIMM banks detected |
| 5 or 6 flashes, pause | Contact Apple or an Apple Authorized Service Provider |