Key Takeaways
- The most common causes of a modem reboot loop are a failing power adapter, overheating, and loose or damaged coaxial cables.
- A factory reset and firmware update will fix most software related reboot issues, while signal problems require a call to your ISP.
- If your modem is more than five years old and reboots persist after troubleshooting, the device is likely failing and should be replaced.
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If your modem powers on, connects briefly, then shuts off and restarts again, you are dealing with a reboot loop. This problem cuts your internet every few minutes and almost always points to one of a small handful of causes. Below are the most common reasons your modem keeps restarting and how to fix each one, in the order you should try them.
Common Causes of a Modem Reboot Loop
- Failing power adapter: The power brick is the single most common point of failure on any modem.
- Overheating: Dust buildup or poor ventilation triggers automatic thermal shutdowns.
- Loose or damaged coaxial cable: A weak signal connection forces the modem to reset.
- Out of spec ISP signal levels: Line issues on the provider side can trigger constant reboots.
- Outdated firmware: Bugs in older firmware versions can cause crash loops.
- End of life hardware: Modems typically last three to five years before internal components fail.
Step by Step Fixes
1. Test the Power Adapter and Outlet
Unplug the modem and feel the power brick (the small black box on the power cord). If it is unusually hot, buzzing, or has any burn smell, it is failing. Try a different wall outlet, ideally one not on a power strip or surge protector that may have worn out. If you have a spare adapter with matching voltage and amperage ratings printed on the label, swap it in. A replacement adapter from the manufacturer is usually under twenty dollars.
2. Check for Overheating
Touch the top of the modem. If it is hot to the touch, that is your problem. Move the modem to an open area away from other electronics, lift it off the floor or shelf so air can flow underneath, and use a can of compressed air to clear dust from the vents. Never stack a router or anything else on top of the modem.
3. Inspect the Coaxial or Ethernet Cable
For cable modems, unscrew the coaxial cable (the screw on round cable) from the back of the modem. Look for a bent center pin, green corrosion, or a loose connector. Hand tighten it back on, then snug it with pliers or a coax wrench. For fiber or DSL modems, reseat the ethernet or phone line. Replace any cable that looks damaged.
4. Remove Splitters
If your coaxial line passes through a splitter (a small metal device that splits one cable into two), bypass it by running the cable directly from the wall to the modem. Splitters cut signal strength and a failing one is a frequent cause of repeated reboots.
5. Factory Reset the Modem
Find the small reset button on the back of the modem, usually a pinhole. With the modem powered on, press and hold the button with a paperclip for thirty seconds, then release. The modem will reboot once and come back with factory default settings. This clears any corrupted configuration that may be causing the loop.
6. Check Your Signal Levels
Most modems have a built in status page you can view in a browser. Connect to your modem and go to 192.168.100.1 for most cable modems. Look at the signal section:
- Downstream power between -7 dBmV and +7 dBmV
- Upstream power between 35 dBmV and 50 dBmV
- Signal to noise ratio (SNR) above 33 dB
Anything outside these ranges is a signal problem your ISP must fix on their end.
7. Update the Firmware
Most ISP rented modems update automatically. If you own your modem, log into the admin panel and check for a firmware update under the administration or system menu. Apply any available update and let the modem reboot.
8. Call Your ISP
If none of the above works, the issue is likely on the provider side. Ask the agent to check for "T3 timeouts," signal levels at the tap outside your home, and whether there are known outages in your area. If their remote diagnostics show problems, request a line technician visit at no charge.
When to Replace Your Modem
If your modem is more than five years old, reboots persist after every fix above, and your ISP confirms the line is clean, the hardware is failing. Buying your own modem also stops the monthly rental fee on your bill, which usually pays back the cost of a new modem within a year.
For replacement recommendations, see our guides to the best modems for Xfinity, best modems for Spectrum, and best modems for Cox.
Frequently Asked Questions
How often should I restart my modem?
Once a month is enough for most users. Restarting more often than that signals an underlying problem that should be diagnosed rather than masked with constant reboots.
How long do modems last before they need replacing?
Most modems last three to five years. Heat, power surges, and ISP technology upgrades all shorten that lifespan. If your modem is older than five years and acting up, replacement is usually more cost effective than continued troubleshooting.
Can a bad coaxial cable cause my modem to keep restarting?
Yes. A damaged, corroded, or loose coaxial cable causes signal drops that force the modem to reset and re-establish a connection with your ISP. Replacing the cable or removing splitters often resolves the issue immediately.
Why does my modem reboot at the same time every night?
Many ISPs push firmware updates or run line maintenance during overnight hours, which can cause a single scheduled reboot. If your modem reboots once at the same time each day and the connection comes back within a few minutes, this is normal. If it loops, contact your ISP.
Can a power surge damage my modem?
Yes. Power surges from storms or grid fluctuations are a leading cause of modem failure and reboot loops. Always plug your modem into a quality surge protector and replace any surge protector that is more than a few years old, since the internal components wear out over time.
Will a factory reset fix a modem reboot loop?
Sometimes. A factory reset clears corrupted settings and forces the modem to re-register with your ISP, which fixes software related reboot issues. It will not fix hardware failure, bad cables, or signal problems on the ISP side.
Should I rent or buy a modem if mine keeps failing?
Buying your own modem is almost always cheaper over the long run. Most ISPs charge ten to fifteen dollars per month for a rental, while a quality owned modem costs between one hundred and two hundred dollars and pays for itself within a year.
