Internet & modems

Modem keeps rebooting itself

A modem that reboots on its own repeatedly usually has a power supply issue, an unstable line signal, or is stuck trying and failing to complete a firmware update, and identifying which helps target the fix.

Difficulty
Easy
Time
15–30 minutes
DIY cost
$0–$20
Pro cost
$0–$100

Symptoms

  • All modem lights go dark then restart in a cycle every few minutes
  • Internet drops briefly every time the modem reboots
  • Reboots happen even with no changes to the network
  • Modem's admin page (if accessible) shows a very short uptime repeatedly

Likely causes

  • CommonFailing or loose power adapterA worn power supply can cause the modem to lose power briefly and restart in a repeating cycle.
  • CommonUnstable signal from the provider causing repeated resync attempts that look like rebootsA marginal or noisy line can cause the modem to lose sync and restart its connection process repeatedly, which can resemble a full reboot.
  • PossibleFirmware update stuck in a failure loopA corrupted or interrupted firmware update can cause a modem to reboot repeatedly trying to complete it.
  • PossibleOverheatingA modem running hot from poor ventilation can shut down and restart as a protective measure.

What to do

  1. Check that the power adapter is fully seated in both the modem and the outlet, and try a different outlet.
  2. Feel the modem's temperature and relocate it to a cooler, well-ventilated spot away from other warm electronics.
  3. Watch a full reboot cycle and note the light pattern, since a pattern stuck on the same light for a long time before restarting can indicate a signal sync problem versus a straightforward power issue.
  4. Check your provider's outage map or call support to rule out a line-side issue causing repeated resync attempts.
  5. If you have a spare power adapter of the correct voltage, test it to rule out a failing original adapter.
  6. Let the modem sit unplugged for a full 2 minutes before plugging back in, to rule out a stuck firmware update state.
  7. If the modem continues rebooting repeatedly after ruling out power and heat, and no outage is confirmed, request a modem swap from your ISP, since this pattern often points to failing internal hardware.

Tools and parts

Replacement modem power adapterSearch: “modem power adapter replacement”

When to call a pro

If the modem keeps rebooting despite good power, ventilation, and no confirmed outage, ask your ISP for a replacement modem, since this is a common sign of failing hardware.

Safety

Generally low risk

Generally low risk for a careful person. Stop if anything looks different from what this guide describes.

Related guides

Operator provides AI-generated troubleshooting information. It can be wrong. For safety-critical, electrical, gas, structural, medical, automotive safety, or other high-risk problems, consult a qualified professional.