If you're having any of the aforesaid Wi-Fi issues on the Galaxy S4, then you may consider checking on the workarounds elaborated in this content.
First, please note that compared to wired connection, wireless signal strength may be overly sensitive, which could trigger error message/prompts. In some cases, it would automatically switch to Mobile data instead of using the available Wi-Fi connection.
Typically, when the Wi-Fi connection is not stable, you will be prompted with an error message. Reports said many Samsung Galaxy S4 devices that run software version Android 4.3 are having Wi-Fi issues.
Here are the suggested methods to fix an unstable Wi-Fi connection on your Galaxy S4 handset. Both the phone and router settings have to be checked in this case.
A. Checking phone settings1. Get to your phone Settings.
2. Select Wi-Fi. This will prompt you with the available Wi-Fi networks in range.
3. Long press on the existing Wi-Fi connection to continue.
4. Now tap on Forget network.
5. Press the Menu key to get to the Advanced setting options.
6. Tap Advanced to continue.
7. Ensure the Passpoint is set to OFF or disabled. Doing so will prevent the phone from automatically connecting to a wireless access points that require additional authentication via web browser.
8. Remove the check mark on the box next to Auto network switch to disable or turn off Auto network feature.
9. Go to your router and do the following steps.
B. Router check1. Check and make sure the router is broadcasting in a clear spectrum, meaning there are no possible signal interferences including other Wi-Fi signals, wireless home phones or microwaves. These things are among the common factors that can influence the router signal. In case your router is installed in areas with greater interference, try to use the 5Ghz frequency instead.
2. When you test your router signal, be sure to do in places without walls and electronics that may break the line-of-sight connection between the router and your phone.
3. If your phone is located far from the router, try to change signal from 5Ghz to 2.5Ghz and see if there are improvements.
For further assistance with router check/settings configuration, please contact your router manufacturer.