How to Tell If Your Modem Is Bad

A bad modem usually shows itself through dropped internet, slow speeds that don't match your plan, or a pattern of needing to restart it multiple times a week. The most reliable sign is that your internet cuts out for 10 to 30 seconds at a time, then comes back on its own—this happens when the modem loses its connection to your internet service provider's network. You can test this by checking your modem's lights: if the internet light (usually labeled "Online," "Internet," or "WAN") is flickering or off when you're not actively restarting, your modem is likely failing.

Another clear indicator is that your speeds are consistently slower than what you pay for, even when you're the only one using the network. Run a speed test on a device connected directly to the modem with an ethernet cable—if it's still slow, the modem is the problem. If speeds are normal on ethernet but slow on WiFi, your modem's wireless radio may be failing instead of the whole unit.

Key Takeaways

  • A modem that needs restarting more than once a week, or that drops your connection for 10 to 30 seconds at a time, is likely failing.
  • Check the internet light on your modem—if it's flickering or off when you're not restarting it, the modem cannot hold a stable connection.
  • Run a speed test using an ethernet cable plugged directly into the modem; if speeds are still far below your plan, the modem is the bottleneck.
  • Modems typically last 5 to 7 years before hardware inside starts to degrade, so age combined with these symptoms is a strong sign of failure.
  • Before replacing your modem, restart it by unplugging it for 30 seconds, then plug it back in and wait 3 to 5 minutes for it to fully boot.

The Restart Test: Your First Troubleshooting Step

Before you assume your modem is bad, do a proper restart. Unplug the modem from power, wait 30 seconds (count it out—this matters), then plug it back in. Do not press a reset button on the back; that erases your settings. Wait 3 to 5 minutes for all the lights to stabilize. During this time, the modem is reconnecting to your internet service provider's network, and this process can take longer than you'd expect.

If your internet works normally for the next few days, the modem was just stuck in a bad state and a restart fixed it. If the same problem returns within a week, or if restarting helps for only a few hours, your modem is likely failing. Write down when the problem happens and how long it lasts—this information helps your internet service provider diagnose the issue if you need to call them.

What the Modem Lights Tell You

Your modem has several lights on the front or back. The one that matters most is the internet or online light, usually labeled "Online," "Internet," "WAN," or shown as a globe icon. When everything is working, this light should be solid green or blue. If it's off, orange, or red, your modem has lost connection to your internet service provider. If it's flickering constantly, the modem is struggling to hold that connection.

The power light should always be solid. If it's off, make sure the modem is plugged in and the outlet works—plug a lamp into the same outlet to test it. The downstream and upstream lights (sometimes labeled "DS" and "US") show data flowing to and from your service provider; they should flicker occasionally when you're using the internet, but not be constantly on. If these lights are off or never flicker, the modem cannot communicate with the network.

The WiFi light shows whether the wireless radio is working. If your ethernet connection is fine but WiFi is slow or drops, and the WiFi light is off or dimmer than usual, the wireless part of the modem is failing while the rest still works.

Speed Tests and What They Show

A speed test tells you whether your modem is delivering the speeds you pay for. Go to speedtest.net or fast.com on a computer or phone, but first plug an ethernet cable directly from your modem to your computer. WiFi can be slow for many reasons that have nothing to do with the modem, so ethernet gives you the clearest picture. Run the test three times over the course of a few minutes and note the results.

Compare your results to the speeds your internet plan promises. If you pay for 100 Mbps read and you're getting 20 to 30 Mbps on ethernet, your modem is likely bad. If you're getting close to your plan speed on ethernet but WiFi is much slower, the modem's wireless radio is the problem. If speeds are fine on ethernet but you have other symptoms like constant disconnects, the modem's connection to the network itself may be failing even though it can still transfer data when it's connected.

How Old Is Your Modem

Modems typically last 5 to 7 years before the hardware inside begins to degrade. If your modem is older than 7 years and you're seeing any of the symptoms described here, age is working against it. Even if it's not completely dead, an older modem may not handle modern internet speeds well, especially if your service provider has upgraded their network since you bought it.

Check your modem's model number (usually on a sticker on the back) and search for it online with the word "release date" to find out how old it is. If it's more than 7 years old and you're having problems, replacement is often the most practical solution. Modems are not repairable—when the internal components fail, the whole unit has to be replaced.

When to Call Your Internet Service Provider

If your modem is showing a bad internet light, dropping connection repeatedly, or failing a speed test, contact your internet service provider before you buy a new modem. They can run a line test from their end to see whether the problem is the modem or the connection coming into your house. They may also have a newer modem they can send you, either for free or for a rental fee, depending on your plan.

Have the modem's model number and serial number ready when you call—both are on the sticker on the back. Tell them exactly what's happening: "The internet light goes off for 30 seconds at a time," or "Speed tests show 25 Mbps when I pay for 100 Mbps." Specific details help them narrow down the problem faster. If they determine the modem is bad, they'll either replace it or tell you to buy your own.

Modem Age and Compatibility With New Plans

Even if your modem is not completely broken, it may be too old to work well with your current internet plan. Internet service providers regularly upgrade their networks to support faster speeds, and older modems cannot take advantage of these upgrades. If you recently switched to a faster plan and your speeds are not improving, your modem may be the limit.

Check your modem's specifications online to see what maximum speeds it supports. If your plan offers 300 Mbps but your modem maxes out at 100 Mbps, you're paying for speeds your modem cannot deliver. In this case, buying a newer modem will actually let you use the service you're already paying for. Your internet service provider's website usually lists which modems work with your plan.

Frequently Asked Questions

How often should I restart my modem?

You should rarely need to restart a healthy modem. If you're restarting it more than once a month to fix connection problems, something is wrong. A modem that needs restarting weekly is definitely failing. Occasional restarts during storms or after a power outage are normal, but regular restarts mean the modem cannot hold a stable connection on its own.

Can a bad modem cause WiFi to be slow but ethernet to be fast?

Yes. If your ethernet connection is fast but WiFi is slow or drops frequently, the modem's wireless radio is failing while the wired connection still works. In this case, you could use ethernet cables to your devices, or replace just the modem. Some internet service providers will swap it out quickly if the wireless part is the only problem.

What's the difference between a bad modem and a bad router?

A modem connects your house to your internet service provider's network. A router takes that connection and shares it wirelessly or through ethernet to your devices. If ethernet speeds are slow, the modem is likely bad. If ethernet is fast but WiFi is slow, the router is the problem. Many people have both in one box, which makes this harder to diagnose.

Is it cheaper to rent a modem from my internet service provider or buy my own?

Buying your own modem is almost always cheaper over time. Rental fees are usually $10 to $15 per month, which adds up to $120 to $180 per year. A good modem costs $100 to $200 and lasts 5 to 7 years, so you break even in one to two years. After that, you own it and pay nothing. Check your service provider's website to see which modems they support before you buy.

Will replacing my modem fix my internet if the problem is the service provider's network?

No. If your internet service provider's network is down or unstable, a new modem will not help. This is why calling your service provider first matters—they can tell you whether the problem is on their end. If they confirm the network is fine and your modem is bad, then replacement will fix it. If the network is the problem, you have to wait for them to fix it.