Troubleshooting modems with multiple status lights

C3510XZ modem lights diagram
C3000Z modem front view with lights

There's a lot of technology behind the blinking lights on your modem. Learn what they mean and what they tell you about your fiber internet connection.

This guide applies to our tower-style modems, including the C3510XZ and the C3000Z (pictured above). If you have a different kind of modem, follow one of the links below.

Note: Depending on your modem model, the lights shown below may have a slightly different appearance or order.

Power light

As soon as the modem has power, it will boot up. Once it has run some hardware tests in the background, the power light will turn solid GREEN. Not green? Click to open options below.

Power light OFF: The modem isn't plugged in or there's another issue with the power.

Power light off (gray)

Power light RED: The modem is running a hardware test. If it's still red after a few minutes, there could be hardware or sofware failure.

Power light red

Power light ORANGE or blinking GREEN/ORANGE: The modem is running a software test.

Power light orange or amber
Power light blinking green and orange

Internet light

Once the modem is powered up, it will search for our network. When it successfully connects to the Quantum Fiber network, the internet light will turn solid GREEN. Not green? Click to open options below.

Internet light OFF: The modem is in 'transparent bridge' mode. If it stays off for more than 30 seconds after the power light turns green, try doing a modem reset.

Internet light is off (gray)

Internet light blinking RED/GREEN: The modem is running its auto-configuration process. If this continues for over a minute, try restarting. If it gets hung up on this step again, you may need to get help from an agent.

Internet light is blinking red and green

Internet light RED: The modem wasn't able to talk to the Quantum Fiber network. This means something is configured incorrectly—you'll need help from a technician to fix this.

Internet light is solid red

Firmware updates

Firmware is the built-in software that makes your modem work. Occasional updates are needed to add new features, fix bugs, and keep the modem running its best. When a firmware update is being installed automatically, you'll see the power light blink to show the update is in progress. This most often happens in the middle of the night.

WAN light

The WAN light will be solid GREEN to indicate a good connection from the Quantum Fiber network terminal (ONT) to your modem. 

WAN light OFF: There is no connection from the network terminal to the modem.

WAN light RED: There is a connection error that will need attention from a technician.

LAN or Ethernet lights

Once you're online, it's likely that you'll connect most of your devices to WiFi. But you may want to use a wired Ethernet connection in some cases. There will be four ports on the back of the modem that you can plug a cord into, labeled either "Ethernet" or "LAN." The LAN light or multiple Ethernet lights on the front of the modem will be solid GREEN only when a device is plugged into the corresponding port on the back.

Ethernet light(s) OFF: No device is connected to the corresponding Ethernet port.

Ethernet light is off (gray)

If you have a device plugged into an Ethernet port, but the light is not on, check these things:

  1. Make sure the Ethernet cord is fully clicked in on both ends. One end will plug into the modem port, and the other end will plug into your desktop computer, game box, or other device.
  2. Try a different Ethernet port if there are more than one. 
  3. Try another Ethernet cable if you have a spare.

Note: The USB port is not enabled on Quantum Fiber modems. You can disregard this light.

WiFi lights

You'll see two WiFi lights (2.4 G and 5 G) for the two different wireless frequencies. These lights will be solid GREEN when WiFi is enabled, and will flash or flicker green whenever data is transmitted over that WiFi network (SSID). 

Wireless light OFF: The modem's WiFi is disabled in the settings. If you have our 360 WiFi mesh system, the WiFi on your modem will be disabled on purpose, to allow the WiFi pods to work.

WiFi light ORANGE: The WiFi network is temporarily turned off based on a wireless schedule created in the modem settings. 

To adjust the WiFi settings on your modem:

  1. Open a web browser on a device that is connected to your modem, and go to the modem settings portal, or GUI at Sign in using the admin username and password on your modem label.
  2. Select the Wireless Setup menu.
  • To enable the WiFi network, select Basic Settings in the left sidebar. Next to 'Wireless Radio,' choose Enable.
  • To change the WiFi schedule, select Wireless Schedule in the left sidebar. Select or update the days and times you want to enable or disable the entire WiFi network.
  1. Select Apply to save your changes.

WPS light

WiFi Protected Setup (WPS) is an easy way to connect devices to your WiFi network. You simply push the WPS button on the modem, then from your device, select the correct network and it will connect without a password. The WPS light will be GREEN when this setting is enabled and ready to connect.

WPS light OFF: WPS is disabled.

WPS light is off (gray)

To enable WPS:

  1. Open a web browser on a device that is connected to the modem, and go to Sign in using the admin username and password on your modem label.
  2. Select the Wireless Setup menu.
  3. Select WPS in the left sidebar.
  4. Select Enable.
  5. Select Apply to save your changes.

WPS button blinking ORANGE: WPS is connecting to a device. If this continues for more than 2 minutes without connecting successfully, it will reset. You can try again to connect to your device. If it doesn't work a second time, try restarting your modem, then try WPS once more.

WPS light blinking amber (orange)

WPS button blinking RED: A connection error occurred. Try again, and if the blinking red continues for more than 30 seconds, try restarting your modem and then attempting the WPS connection again.

WPS light blinking red

If you've tried restarting and repeatedly can't get the WPS connection to work, you can chat with an agent for more troubleshooting assistance.


If one of the status lights on your modem isn't behaving, that might indicate a problem. Based on the descriptions above, you can identify a possible issue, which could be a problem with the equipment itself or with the fiber network.

Here are some things you can try:

  1. Make sure you are using the correct power supply (the one that came with the modem).
  2. Try restarting your modem if you haven't already, and be sure to wait at least 30 seconds before plugging it back in.
  3. Check to make sure your modem isn't overheating. It should be in a place with good air circulation, at least 2 to 3 feet away from any sunny windows or heat vents.
  4. Make sure the modem is getting enough power. If you have a lot of devices using the same outlet as your modem (like it's plugged into a power strip with several other things) try plugging it directly into a power outlet with no more than one other device plugged in. 
  5. As a very last resort, try resetting your modem to the factory default settings.

Need more help? Chat with us! Find the purple chat bubble in the lower right corner of this screen, or chat from the Quantum Fiber app or our online portal. If you prefer to call or email, you can do that too.