UniFi Access Point Not Powering On: Troubleshooting Guide

For UniFi access point not powering on troubleshooting, the cause is usually power delivery rather than a dead AP. Check five things in order: the switch port actually sources PoE, the PoE standard matches the model (a U7 Pro needs PoE+), the switch has spare budget, the cable carries all four pairs, and any injector is wired LAN-in, POE-out.

Only when the AP stays dark on a known-good PoE+ source with a short patch cable is it time for TFTP recovery or an RMA. A factory reset does nothing for a device with no power, and swapping in a new AP before testing the port just moves the fault into a new box.

Quick triage by symptom

Ubiquiti’s LED status guide reads steady white as ready for adoption and steady blue as configured. Either way the AP is powered, so the UniFi adoption failed guide is the right path, not this one.

Does the switch port actually supply PoE?

Not necessarily, and it is the cheapest thing to rule out. Check the port before you touch the AP:

• Non-PoE ports on a PoE switch. The USW-Lite-8-PoE has eight gigabit ports, but only four are PoE+, sharing 52 W. An AP on one of the other four gets no power at all.
• Switches that consume PoE rather than source it. The USW-Flex-Mini takes PoE or 5 V USB-C as input and lists no PoE output. An AP behind one needs its own injector.
• Port PoE mode set to Off. In UniFi Network, open the switch, select the port and read its PoE setting; UniHosted’s PoE troubleshooting guide lists Auto, Off or a specific type. Use Auto for 802.3af/at APs.
• 0 W on the port. Zero watts with the AP connected means the switch is not delivering power, either because the AP is not requesting it or the port is not offering it. Moving the cable to another PoE port separates the two.

To read the PoE controller directly, SSH to the switch:

swctrl poe show id 1-8
swctrl poe restart id 3

show prints each port’s Class, PwrGood, Power(W), Voltage(V) and Current(mA); restart power-cycles one port. Keep the id keyword. A write-up on a USW-Lite-16-PoE documents swctrl poe set off 6, typed without id, cutting PoE on every port and taking the APs down with it.

Does the PoE standard match the AP?

It has to match on both watts and volts. Current UniFi APs take standards-based PoE at 44 to 57 V. 802.3af delivers 12.95 W at the powered device and 802.3at delivers 25.5 W, per the IEEE figures summarised on Wikipedia. Set that against Ubiquiti’s published maximum draw:

Three mismatches account for the classic “new AP, no lights” call:

1. PoE+ AP on an af source. A U7 Pro’s 21 W maximum is well above the 12.95 W an af port delivers. Whatever the exact symptom, an af port or af injector is the wrong source. Move it to an 802.3at port or a PoE+ injector.
2. Modern AP on a 24 V passive injector. The 24 V brick that shipped with an AC-series AP sits far below the 44 V floor of the U6 and U7 range. It will not run them.
3. Legacy passive AP on a standards port. An 802.3af/at switch looks for a 25 kΩ detection signature before applying power, and passive PoE does no negotiation. The original UAP-AC-LITE quick start guide lists passive 24 V only, so an af/at-only port is the wrong source for that hardware. Later revisions may differ; check the label.

If you solve the third case with a switch port set to passive 24 V, label that port and never move 802.3af/at gear onto it. Passive PoE applies voltage without checking what is connected, which is how equipment gets damaged.

Is the switch out of PoE budget?

It is if the AP powers up alone but drops when another device is added. Ubiquiti publishes a total PoE availability separate from the per-port rating, and the total is the binding limit. The USW-Lite-8-PoE allows 30 W per port but 52 W across its four PoE+ ports: three U7 Pros at their 21 W maximum come to 63 W, so every port is individually fine and the switch is still 11 W short.

Budget failures show up as stable APs rebooting after a camera is added, or the last device plugged in never starting. Check PoE usage in the switch’s device panel, unplug the newest load and watch whether the AP recovers. Then size the fix with the AP PoE budget and switch planning worksheet: a larger PoE switch or one PoE+ injector, not a firmware update.

Is the cable carrying power?

Not always, even when it passes data. UniHosted notes that damaged or poorly crimped cable can block PoE while a link stays up. The passive scheme in the AC Lite guide puts power on pairs 4,5 and 7,8, so a run with only two pairs terminated can never power that AP. Standards PoE is sensitive to loop resistance too: Type 2 (802.3at) assumes Category 5 at no more than 12.5 Ω, against 20 Ω for Type 1, so a long or badly terminated run can carry an af load and fail at PoE+.

The test is mechanical:

1. Take the AP down and connect it to the same PoE port with a short factory patch cable.
2. If it boots, the AP and port are fine; the in-wall run, keystone, patch panel or an inline coupler is the fault.
3. Put a continuity tester across all eight conductors and re-terminate any end with an open or swapped pair.

Is the injector wired backwards or faulted?

Check the jacks first, because they are not interchangeable. Ubiquiti’s U6-Mesh quick start guide says to connect the AP’s cable to the adapter’s POE port and your LAN to its LAN port. Reversed, the AP sits on the unpowered side.

Match the injector to the AP: 802.3af for a U6 Lite, 802.3at for a U7 Pro, U6 Enterprise or U7 Pro Max, and never a 24 V passive unit for anything rated 44–57 V.

A blinking injector status LED signals a fault on the output side. On the UAP-AC-LITE, iFixit documents an over-voltage TVS diode (SMBJ24A at D6) whose expected failure mode is a short, which the injector detects and refuses to power. A shorted diode reads under 1 Ω in both directions. That is an out-of-warranty repair, and iFixit warns that leaving the diode out exposes the board to the next overvoltage event.

What if it stays dark on a known-good PoE+ source?

Then it is firmware or hardware, and the LED tells you which. If it lights but loops or never finishes booting, try a factory reset first: hold Reset for more than five seconds with power applied, as the AC Lite guide specifies. If that fails, use TFTP recovery.

Ubiquiti’s recovery mode procedure: hold Reset, apply power, and keep holding until the LED cycles white, blue, off. The AP then answers at 192.168.1.20. Download the model’s firmware .bin, give your laptop a static address in the same /24 and push it:

# laptop at 192.168.1.25/24, on the injector's LAN side or the same VLAN
tftp 192.168.1.20
tftp> binary
tftp> rexmt 1
tftp> timeout 60
tftp> put firmware.bin

Purple Computing’s walkthrough notes the button can take up to 25 seconds to reach recovery mode and that the AP reboots itself after a successful transfer, so leave power alone while it writes.

If there is no LED at all on two known-good sources, or it never enters recovery mode after several attempts, treat it as hardware. Open a warranty claim with Ubiquiti support and include the model, serial number and the ports, PoE standards, cables and injectors you tested.

Confirm it stays up

Once it lights, watch it for a day before closing the ticket. If its uptime resets while the switch logs the port bouncing, power is still marginal; go back to the budget and cable checks. If it stays up but never appears in UniFi Network, that is adoption, not power. When planning the next AP, the UniFi home network setup guide covers what to buy first so PoE capacity is in the plan from day one.

FAQ

why is my unifi ap light off

Either the AP has no power or its LED has been disabled in UniFi Network. Check the switch port first: a non-zero power draw and connected clients mean the AP is running with LEDs off. A 0 W reading means the port is not sourcing PoE, so check its PoE mode, the cable and the injector.

will a u7 pro work on 802.3af poe

No. Ubiquiti specifies PoE+ for the U7 Pro, with a maximum draw of 21 W, while an 802.3af port delivers 12.95 W at the device. Use an 802.3at port or a PoE+ injector. The same applies to the U6 Enterprise at 22 W and the U7 Pro Max at 25 W.

can i use an old 24v ubiquiti injector on a u6 lite

No. The U6 Lite’s specified input range is 44 to 57 V DC, so a 24 V passive injector from an older AC-series kit cannot run it. Use an 802.3af or 802.3at switch port or injector instead, and keep the 24 V brick for the legacy passive hardware it shipped with.

how do i know if my unifi access point is dead

It is probably dead if it stays dark on two known-good PoE+ sources using a short factory patch cable and never enters TFTP recovery mode after several attempts. Before that point, the port, PoE standard, budget, cable or injector are more likely culprits. Record each test before opening a warranty claim with Ubiquiti.

why does my unifi ap keep rebooting

A UniFi AP that reboots on its own is usually short on power: an 802.3af port feeding a PoE+ model, a switch past its total PoE budget, or a marginal cable run. Compare the model’s maximum draw with the port standard and the switch’s remaining budget, then retest on a short patch cable.