WIFI Problem

[Aamosh]

Hello to the Android World,
I am on Samsung Galaxy S3 running on android 4.3 . My problem is that the S3 detects the WIFI, scans it from every part of the house perfectly fine. But it only gets connected when I am in the same room as the router. Whenever I move away from the room containing router, the device shows the internet as only saved and secured and does not get connected. I mean it only happens with my device, other all device works perfectly fine from every part of the home. Also this problem does not only happen with my home wifi it happens with every wifi.
Things I have already tried doing.
1) Factory reset the S3.
2) Use custom frimwares.
3) Use apps such as wifi analyzer, wifi fix.
Please help me get past this problem.

 

[svim]

Just going by your description I'm going to take a wild guess that something has happened with the internal antenna. Considering how proximity appears to be the central issue your WiFi issues maybe (knock on wood) it's just a matter where the antenna connector needs to be re-seated. If you follow this guide:
https://www.ifixit.com/Teardown/Samsung+Galaxy+S+III+Teardown/9391
in step 6 you'll see a white wire that runs along the length in a shallow channel. Try removing and re-attaching the connector end. See step 20 in this link for a better description of the connector:
https://www.ifixit.com/Guide/Samsung+Galaxy+S+III+Motherboard+Replacement/12696
This whole process does require some disassembly of your S3 but the most significant step is removing the plastic midframe cover, you don't need to actually remove components, you just want to take a look at the antenna.