iMac 27", Mid 2011 : Wi-Fi Connected, But No Internet

Please test after taking each of the following steps that you haven't already tried. Stop when the problem is resolved. Back up all data before making any changes.

Step 1

Take the applicable steps in this support article.

Step 2

The Wireless Diagnostics program generates a large file of information about your system, which would be used by Apple Engineering in case of a support incident. Don't post the contents here.

Be sure to test on more than one Wi-Fi network, if at all possible. A desktop computer can be tested with a mobile hotspot, such as the hotspot created by a cell phone. If the problem only exists on one network, then the access point of that network should be the focus of your attention, not the computer.

Step 3

If your model supports AirDrop (most do), open the AirDrop window and select

Allow me to be discovered by: No One

Step 4

Disconnect all USB 3 devices, and also all external displays if the Mac has one built in. If you don't know which devices are USB 3, disconnect all USB devices except keyboard and mouse.

Step 5

If you're not using a wireless keyboard or trackpad, disable Bluetooth by selecting Turn Bluetooth Off from the menu with the Bluetooth icon. If you don't have that menu, open the Bluetooth preference pane in System Preferences and check the box marked Show Bluetooth in menu bar. Test. If you find that Wi-Fi works better with Bluetooth disabled, you should use the 5 GHz Wi-Fi band. Your router may not support it; in that case, you need a new router.

Step 6

Open the Energy Saver pane in System Preferences and unlock the settings, if necessary. Select the Power Adapter tab, if there is one. Uncheck the box marked

Wake for Wi-Fi network access

if it's checked.

Step 7

Open the Network pane in System Preferences and make a note of your settings in the Wi-Fi service. It may be helpful to take screenshots of the various tabs in the preference pane. If the preference pane is locked, unlock it by clicking the padlock icon and entering your administrator password. Delete Wi-Fi from the service list on the left by selecting it and clicking the minus-sign button at the bottom. Then recreate the service by clicking the plus-sign button and following the prompts.

Step 8

In the Wi-Fi settings, select

Advanced... ▹ TCP/IP ▹ Configure IPv6: Link-local only

Click OK and then Apply.

Step 9

Reset the System Management Controller.

Step 10

Reset the PRAM.

Step 11

Launch the Keychain Access application. Search for and delete all AirPort network password items that refer to the network. Make a note of the password first. Turn Wi-Fi off and then back on. You'll be prompted for the password when you reconnect. Save it in the keychain.

Step 12

Disconnect all wired peripherals except those needed to start up, and remove all aftermarket expansion cards, if applicable. Start up in safe mode and log in.

Note: If FileVault is enabled in OS X 10.9 or earlier, or if a firmware password is set, or if the startup volume is a software RAID, you can’t do this. Ask for further instructions.

Safe mode is much slower to start up and run than normal, with limited graphics performance, and some things won’t work at all, including sound output. The next normal startup may also be somewhat slow.

The login screen appears even if you usually login automatically. You must know your login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.

Test while in safe mode. If the problem is (temporarily) resolved, stop here and post your results.

Step 13

Reinstall the OS. The linked support article refers to OS X 10.11 ("El Capitan"), but the procedure is the same for OS X 10.7 ("Lion") and later. You may need an Ethernet connection in order to carry out this step.

Step 14

Make a "Genius" appointment at an Apple Store, or go to another authorized service center.

Hello,

I'm having the same issues with the same device (iMac mid 2011, 27", 3,1 ghz) and i have these endless issues since i switched to Yosemitethe first day on release day one.

I've followed countless tutorials with more or less success. Even reinstalling the OS from scratch doesn't work. Even if i can have weeks of rest, it come back again at some point and sometimes having drops multiple times per hour ! Only temporary solution : use ethernet or deactivate/activate wifi.

All devices at home are working seamlessly (iPhone 5C, iPad Air, Apple TV2, my previous PC, my raspeberry Pi2, my wife's Android phone etc etc) My Wifi hardware only is having issues.

I'll try the steps i didn't try yet but just don't copy paste pre formatted anwsers :step 3 and 4 are non applicable since our iMacs don't have USB3 nor AirDrop.

Thanks for the help anyway and i really hope a fix from Apple on this.

Thanks for the advice, but i'm living in a small town with only one other network outside of mine around.

And most of all, my router (supplied by my ISP, i'm in France) doesn't support 5ghz, so i can't try. All i can say is prior to updating to Yosemite and el capitan, it worked well

Just because the only WiFi around is yours doesn't necessarily mean that the frequencies aren't crowded. Many other devices can use the same frequencies including cordless phones, baby monitors, and other items.

If you have the same router that you've "had for years", a new with with a 5GHz band might be just what you need. It made a MASSIVE difference in my home and I live in a very rural area.

The-Big-K wrote:

Right! The only downside is that the 5GHz range is very limited. That can be fixed using a good range extender. But speed and overall connectivity is just cool!

Very true. The "far ends" of my house are not well-covered by the 5GHz. But, that's basically the garage at one end and my office at the other (where I have a lot of my computing equipment and a secondary router anyhow).

ok ok i understand. Thanks to all.

What annoys me is that the only cause of those issues is my iMac software only. I'm just so disappointed that my 10years old dusty, Win7, 300$ pc is working better in wifi than my 1900$ 2011 iMac !

I'll try with a wifi dongle i have for my raspberry (it seems compatible) just in case.

Honestly, i don't want to buy a new router (even if it's not that expensive), not being sure that it will solve the problem, because Apple don't want to solve issues that i'm not the only customer to have, but it seems i have no other choice.

As a point of reference - I had a Windows laptop and a MacBook Air in the house that were working just fine (along with an older Lenovo machine, too). All of the mobile devices, especially the iPads, would suffer heavy lag, disconnects, and generally poor performance. Updating the router absolutely solved everything.

I can appreciate the sentiment of not wanting to spend money and undertake effort that don't know will solve a problem. That's why stores have return policies, though.

The other thing you could try would be to enable the WiFi monitor on your device while you're using it and then look to see if it shows any specific issues that are occurring when you're having the timeouts and such. There's a reasonably good chance that a newer router, with better capabilities, is going to solve a lot of issues for you, though.

I can try.

I understand that the new router for you solved your issues. It was indeed the right solution.

On my side, when my wifi drops on my iMac, all my other devices are still working well and i still have 100% performance.

Only my mac can't connect anymore without restarting Wifi, and it occurs mostly when i'm uploading/downloading (i'm a big twitch user, as watcher and streamer)

My issues were typically ONE device that was being impacted and not my entire WiFi network.

yea but my iPhone 4 says im connected to my home network but when i go on safari its says im offline