Wireless problems on iMac I have an old iMac running OS X Lion, and I am experiencing some Wi-Fi problems. Networks around me are either completely undetectable, or only one of them shows (not the one I own).

My Wireless card is an Airport Extreme BCM43xx. The ioreg -l | grep 14e4 command shows that the card is specifically 14e4:4328.

If it is a firmware problem, then is there any firmware I can install? I only know b43, which might be linux only. Note that wireless does not work in Recovery HD either.
Try changing the channel of your WiFi router. Might fix confusion of the AirPort. To do, see the documentation for your router, for suggestions as to which channel you should choose, option-click the wifi button in the status bar, click Wireless Diagnostics, and then after the application opens, click window, and Scan. This will tell you the best channel to choose for your router.


If changing the channel doesn't fix the issue, try running the Apple Diagnostics Tool. 

OR

If your iMac is pre-2013, try the Apple Hardware Test after completing the steps above with the exception of the Diagnostics tool.