UniFi switch PoE not working: Diagnosing and fixing issues

Your UniFi switch is up, your devices are plugged in, and everything looks good, until you realize your access point or camera isn’t powering on. If you’re staring at a dead UniFi device connected to a PoE port, this guide is for you.

Let’s figure out what’s going on and how to get it sorted.

(Let's dive in !!

First, understand how PoE works on UniFi switches

UniFi switches support multiple types of PoE (Power over Ethernet). The most common are:

• PoE (802.3af) – Standard power for most UniFi APs and smaller devices.
• PoE+ (802.3at) – Higher power for some cameras or heavier APs.
• 24V Passive PoE – Legacy support for older UniFi gear.

Your switch model decides what PoE options are available. Some UniFi switches only support 802.3af/at, while others (like the older 8-port switches) support 24V Passive PoE on select ports.

Mismatch the PoE type and your device won’t power up.

Step-by-step: Diagnose why PoE isn’t working

Let’s walk through the process of troubleshooting a PoE issue. Start with the basics, then dig deeper.

1. Check the PoE compatibility of your device

Go to the device specs and confirm what kind of PoE it needs. For example:

• UniFi U6 Lite – Needs 802.3af
• UniFi G4 Bullet Camera – Needs 802.3af
• Older UniFi AC LITE AP – Can run on 24V passive (older ones)

Make sure your switch supports the same standard.

2. Confirm the switch port is actually providing PoE

In the UniFi controller:

• Go to Devices > Switch
• Click the port where your device is connected
• Check the PoE setting (Auto / Off / Specific type)

Make sure PoE is set to Auto or the correct standard. If it says Off, change it.

3. Look at port status and power draw

Still in the UniFi controller:

• Open the Port Settings or Insights
• Look at the Wattage being drawn on the port

If it shows 0W, the switch isn’t powering anything. Either the device isn’t requesting power or the port isn’t supplying it.

4. Try a different port

Move the cable to another PoE port on the switch. If it powers up there, the first port might be faulty or misconfigured.

5. Swap the cable

Damaged or poorly crimped Ethernet cables can block PoE. Even if the device shows a network link, power might not be getting through. Try a known-good Cat5e or Cat6 cable.

6. Power budget problems?

Some UniFi switches have a total PoE budget. If you’ve got too many high-power devices plugged in, the switch may stop powering some of them.

Check:

• Switch Specs (e.g., 60W, 150W PoE budget)
• How many PoE devices are connected
• Total watts being used

You’ll find this info in the controller under the Device > Details tab for your switch.

If you’re over budget, try unplugging something else and see if the dead device comes back.

7. Check for firmware issues

Outdated switch firmware can cause strange behavior, including PoE not working correctly. In the controller:

• Go to Settings > System > Updates
• Look for updates for your switch
• Apply them and reboot if needed

Always keep UniFi switches up to date. It fixes bugs and improves stability.

8. Restart the switch

Sometimes, a reboot is all it takes. In the controller:

• Click your switch
• Go to Settings > Manage
• Hit Restart

Wait a minute or two and check if the device powers on afterward.

9. Try a PoE injector

As a final test, unplug the device from the switch and power it using a standalone PoE injector (make sure it matches the required PoE standard). If the device powers on, your switch or its configuration is the issue.

If the injector doesn’t work either? The device may be faulty.

Common scenarios and how to fix them

Scenario 1: UniFi AP not powering on from switch

• Check if PoE is enabled on the port.
• Make sure the switch supports 802.3af/at.
• Swap cable and port.
• Confirm firmware is current.

Scenario 2: 24V Passive device not powering

Many new UniFi switches don’t support 24V Passive anymore. If you’re using older UniFi gear:

• Check if the port supports passive PoE.
• If not, use a 24V PoE injector.
• Or consider replacing the device.

Scenario 3: Some devices power on, others don’t

You may have hit your switch’s PoE budget.

• Look at total power usage in the controller.
• Remove a device and see if another turns on.
• Upgrade to a switch with a higher PoE budget if needed.

Scenario 4: Device powers on but drops offline later

• Inspect logs for PoE overloads or errors.
• Replace the cable.
• Consider using a managed PoE switch to better monitor power usage.

Preventing PoE issues in the future

A few small steps can save you hours of troubleshooting:

Use quality Ethernet cables

Stick to Cat5e or Cat6, and avoid cheap pre-crimped stuff. Poor cable quality causes weird PoE problems.

Know your switch’s PoE budget

Plan your devices around it. Don’t max out a 60W switch with five high-power APs and expect perfect results.

Keep firmware updated

Switch updates fix bugs, especially power-related ones. Make it a habit to check for updates every couple of months.

Label your ports

If you manage multiple sites or devices, label which port powers what. That way, it’s easier to know what to check if something dies.

When to consider replacing your switch

If you’ve gone through all the steps above and you’re still seeing problems, it might be time to replace the switch, especially if:

• Multiple ports are failing
• PoE randomly stops working
• The switch runs hot or keeps crashing
• It doesn’t support PoE+ or 802.3bt, and you’re adding higher-demand devices

Sometimes, the easiest fix is upgrading to a newer model with a bigger power budget and better compatibility.

Final thoughts

PoE issues can be frustrating, but they’re usually fixable with a few checks. In most cases, it’s a misconfiguration, bad cable, or the wrong PoE type. Just take a methodical approach: test ports, check settings, and make sure your devices are matched with your switch’s capabilities.

And if you're managing client networks, consider using a hosted UniFi controller to make remote troubleshooting easier. At Unihosted, we handle the controller side so you can focus on the gear. It’s safer, more reliable, and takes one more headache off your plate.