The short answer
Check the power supply first, because a failing adapter is the most common cause and the cheapest to replace. Then check for heat, look at the router’s log for a reason, and update the firmware. If the router restarts at the same time every day, something is scheduled, either by you or by your provider.
A router rebooting itself drops every device in the house for a minute or two, which is disruptive out of proportion to the underlying fault. The causes are a short list, and most of them are cheap to fix once identified.
Cause 1: the power supply
Router power adapters are built to a price and they degrade. As capacitors age, the supply cannot maintain voltage under load, and the router resets when demand peaks, for example when several devices connect at once or a large transfer starts.
Signs pointing at the supply:
- Restarts correlate with heavy use rather than idle periods.
- The adapter is warm or buzzing.
- The router is several years old and has never had a replacement supply.
- Restarts became more frequent gradually over months.
A replacement adapter with the correct voltage, adequate current and the correct plug polarity is inexpensive. Match the voltage exactly and the current rating at or above the original.
Check polarity as well as voltage when buying a replacement adapter. Most equipment uses centre-positive, and connecting a centre-negative supply can damage the router permanently. The symbol is printed on the original adapter and on the router’s socket.
Cause 2: heat
Routers have no fan and rely on convection. In a cupboard, on carpet, stacked under a modem or in direct sun, they overheat, and thermal protection triggers a restart.
The pattern is distinctive: restarts happen more in summer, more when the heating is on, and more after the router has been running for hours rather than immediately after a restart. Moving it into the open, off carpet, unstacked and dust-free resolves it, and raising it slightly on small feet helps models that vent through the base.
Cause 3: firmware
Firmware bugs cause reboots, particularly memory leaks that accumulate until the router runs out and restarts. The signature is a restart roughly every few days at an interval that stays consistent regardless of what you are doing.
Update the firmware. If you are already current and the problem persists, check the manufacturer’s forums for your model, since this is the sort of fault that gets discussed and sometimes fixed in a later release. On an ISP-supplied router, report it, because they can push firmware.
Cause 4: something is scheduled
- A scheduled reboot in the router’s settings, which some models enable by default and many people set up years ago and forgot.
- Provider-initiated firmware updates, typically overnight on an ISP-supplied box.
- A smart plug with a schedule, if the router is plugged into one.
- A timer switch from a previous occupant or a previous purpose.
A restart at exactly the same time daily or weekly is almost always one of these rather than a fault.
Cause 5: the line rather than the router
On some connections, the router restarts when the line drops and resynchronises. That looks like a router problem and is a line problem. Check the router’s log for entries about the connection dropping before the restart, which distinguishes the two clearly.
If the line is dropping, that is a provider matter. Log the times, check whether they correlate with weather or with a particular time of day, and present the log rather than a general complaint.
Most routers keep a system log, usually under Status, System Log or Administration. It will often state the reason for the last restart, whether that was a power event, a watchdog timeout, a firmware update or a manual reboot. Reading it takes two minutes and saves a great deal of guessing.
Cause 6: load
An older router with a weak processor can be overwhelmed by the number of devices in a modern home, by a device making very many connections such as a torrent client, or by features like traffic analysis running on hardware that cannot sustain them.
Symptoms include restarts under load, sluggish admin pages, and improvement after disconnecting devices. Turning off resource-heavy features such as deep packet inspection, parental control filtering and traffic statistics is worth trying. If that helps, the router is at its limit and replacement is the real answer.
Diagnosing efficiently
Read the system log
It often names the cause directly, which makes everything else unnecessary.
Note the timing pattern
Same time daily means scheduled. Under load means power or processor. Every few days regardless means a memory leak. Hot weather means heat.
Move it into the open and off carpet
Free, and it eliminates the heat hypothesis.
Try a different power adapter
Correct voltage, polarity and adequate current. Cheap, and it eliminates the most common hardware cause.
Update the firmware
And check whether your model has a known reboot issue.
Factory reset and reconfigure by hand
Restoring a saved configuration can restore the problem with it. Configuring from scratch once rules out a corrupted setting.
Can a bad power supply cause a router to reboot?
Yes, and it is the most common hardware cause. Ageing adapters cannot hold voltage under load, so the router resets when demand rises. Replacement adapters are inexpensive.
Why does my router restart at the same time every night?
Something is scheduling it: a setting in the router, a provider firmware update window, or a timer or smart plug it is connected to. Check the router’s scheduled reboot setting first.
Is it normal for a router to need restarting regularly?
No. A router should run for months without intervention. Needing a weekly restart is a symptom of heat, firmware problems or ageing hardware.
Could too many devices cause reboots?
On an older router, yes. Consumer routers become unstable somewhere between thirty and fifty clients, and features like traffic analysis make that worse.
How do I know if it is the router or the line?
The router’s log will show whether the connection dropped before the restart. A line drop followed by a resynchronisation is a provider issue; a watchdog or power event is the router.
The order
Read the log, then match the timing pattern to a cause. Move the router into the open and off carpet. Try a replacement power adapter, matching voltage and polarity. Update the firmware and check for known issues with your model. Turn off heavy features if the router is old. And if the log shows the line dropping first, take it to your provider with the times written down.
