Internet & modems

Modem-router combo unit isn't working right

A single combo device handling both modem and router duties can develop problems specific to either function, and isolating which side is failing (internet signal versus Wi-Fi/local network) determines the right fix.

Difficulty
Moderate
Time
15–30 minutes
DIY cost
$0–$150
Pro cost
$0

Symptoms

  • Both Wi-Fi and internet access seem affected together
  • Wi-Fi works locally between devices but nothing reaches the internet
  • Combo unit's lights show a mix of normal and abnormal indicators
  • Provider blames the router function while router troubleshooting doesn't help

Likely causes

  • CommonThe modem portion has lost signal from the provider while the router portion still functions locallyThis creates the appearance of a 'router problem' (like normal Wi-Fi) while the real issue is upstream.
  • CommonCombo unit needs a restart, same as separate modem and router wouldA single restart addresses both functions since they're in one device.
  • PossibleFirmware issue affecting one function but not the otherA partial software fault can impact Wi-Fi, for example, while leaving the internet connection itself fine, or vice versa.
  • PossibleCombo unit aging and one of its two functions is failingThese devices can develop a hardware fault in the router chip or modem chip independently.

What to do

  1. Restart the combo unit fully by unplugging it for 30 seconds and waiting several minutes for it to reconnect after powering back on.
  2. Check the specific lights for internet/online status separately from the Wi-Fi/wireless status light, since this tells you which function is having trouble.
  3. If the internet light is red or off but Wi-Fi devices connect to each other locally, the issue is with the modem side (provider connection), not the router side.
  4. If the internet light looks normal but devices can't get a stable Wi-Fi connection, the issue is likely with the router side of the combo unit.
  5. Check for a firmware update in the device's admin page or app, since combo units get firmware updates just like standalone equipment.
  6. Consider adding your own separate router connected to the combo unit (with the combo's Wi-Fi turned off) if the router side keeps failing while the modem side is fine, giving you more control and often better Wi-Fi performance.
  7. If the modem side of the combo keeps failing, contact your ISP, since it's often leased equipment they can swap out.

Tools and parts

Standalone Wi-Fi routerSearch: “wifi router”

When to call a pro

If your ISP-leased combo unit is repeatedly failing on either side, ask them for a replacement unit at no cost, which is standard for leased equipment issues.

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.