PoE device (camera/AP/phone) not powering up
A Power-over-Ethernet device (IP camera, wireless AP, VoIP phone) won't power on over its data cable — pointing at the PoE source, the budget, the cable, or the device's PoE class.
Safety first
PoE energises the data pairs — generally low risk, but treat the cabling carefully and don't connect non-PoE equipment to a forced-injector incorrectly.
Isolate, lock out / tag out, and prove dead before working unless a live test is specifically required, authorised, and carried out under proper supervision. Always follow local regulations, your site procedures, and the equipment manufacturer's documentation.
Full detail — causes, the why, and common mistakes.
Likely causes
Ranked from most to least likely.
- 1
Switch port not providing PoE / disabled
Most likelyThe port isn't a PoE port, PoE is disabled, or the switch's PoE budget is exhausted.
- 2
PoE class/standard mismatch
#2The device needs more power (higher PoE class/standard) than the source provides.
- 3
Cable fault / excessive length losing power
#3A poor run or excessive length drops too much voltage to power the device.
- 4
Faulty injector / midspan
#4A separate PoE injector has failed or isn't inline correctly.
- 5
Faulty device
Least likelyThe device's PoE input has failed.
Reports are saved on this device to reflect what you actually find.
Testing sequence
Work through one test at a time. Expected reading and what each result means.
Confirm the source provides PoE (right port/injector, enabled) and the PoE budget isn't exhausted.
An enabled PoE source with budget available.
Source provides PoE — check class match and the cable.
No PoE / budget exhausted — enable PoE / free up budget / use a suitable injector.
View all expected readings at once
Fault-finding flowchart
The same logic as a decision tree.
- 1start
PoE device not powering
→ step 2 - 2decision
Does the source provide PoE with budget available?
Yes→ step 3No→ step 4 - 3decision
Does the source meet the device's PoE class/standard?
Yes→ step 5No→ step 6 - 4result
Enable PoE / free budget / use a suitable injector.
- 5decision
Does the device power on a known-good PoE port/lead?
Yes→ step 7No→ step 8 - 6result
Class mismatch — use a source that meets the device's needs.
- 7result
Original run/port at fault — test/repair the cabling.
- 8result
Device PoE input faulty — replace.
Common mistakes apprentices make
- Assuming any port supplies PoE.
- Overlooking an exhausted PoE budget on the switch.
- Class/standard mismatch (device needs more power).
- Ignoring cable length/quality dropping power.
When to stop & escalate
Switch PoE config/budget is usually the network team's area; cabling faults the cabling installer's. A faulty device goes back to its supplier/installer.
If you're past your competence, authorisation, or the safe limits of the job — stop and hand it on. There's no fault worth getting hurt over.
Related faults
Data outlet has no link / no network
A device plugged into a data outlet gets no link or no network, while others work — pointing at the patch lead, the outlet termination, the cable run, or the patch panel/switch port.
Data cabling run fails certification / wiremap fault
A structured cabling run fails a tester (wiremap fault, open, short, split pair, or excessive length) — so it won't reliably carry the network even if a link sometimes appears.
Data connection slow, dropping, or unreliable
A data point links but is slow, drops out, or negotiates a low speed — pointing at cabling quality, a marginal termination, interference, or the run length, rather than a hard break.