OSX Yosemite Wi-Fi: no hardware installed

In some cases, this issue is caused by a hardware fault. A loose connection, a short circuit, or a microscopic break in a solder joint may open and close depending on temperature, making the failure intermittent.

Test after taking each of the following steps that you haven't already taken. Back up all data before making any changes.

1. If you can connect to the Internet via Ethernet, Bluetooth, or a USB network device, make sure all available OS X updates are installed. If Wi-Fi is your only means of network access, skip this step.

2.. There are a few reports that the problem was solved by unchecking the box marked

Wake for Wi-Fi network access

in the Power Adapter tab of the Energy Saver preference pane. I can't confirm.

3. Reset the NVRAM.

4. Reset the System Management Controller.

5. Start up in Recovery mode. In the menu bar of the OS X Utilities screen, there's a Wi-Fi menu. Try to connect. If it works, select Install OS X. If your Mac was upgraded from an older version of OS X, you’ll need the Apple ID and password you used to upgrade, so make a note of those before you begin.

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

The ONLY thing that "fixed" this is on my Mac Air is to run a hardware test (or whatever it is called now). The test will be negative (no hardware problems), but whatever it does software-wise reactivates the wifi card. The problem is that the card could re-lock sometime during the next startup period, or the wifi could go down again after a subsequent startup period. This is clearly a software issue, but I am not sure what. Some people have suggested AirDrop related issues, but I simply don't know whether that makes sense or not. Again, the hardware test method is useful because it allows the App Store to work again--thus, you can go ahead and install updates. Otherwise, for internet purposes, you're relegated to ethernet or plug-in "wifi" cards (though Bolse hasn't released the 10.10 drivers and the 10.9 ones do not work--support said six weeks, but we're well past that now).

No. I do not mean resetting the SMC, nor resetting the PRAM. The SMC and PRAM strategies used to work in Mavericks, but was seemingly eliminated as an effective strategy after one of the last Mavericks updates. What I mean is to run a hardware test: http://support.apple.com/en-us/HT201257. This strategy works at restarting the wifi card each and every time, as long as you run the extended test (the quick test is not sufficient). The reset won't necessarily last long, but it allows you to update your software (at least while connected to an ethernet connection). I did this hardware test reset today, in order to update to the new Keynote, Pages, and Numbers software. This is the only thing that has consistently and reliably worked on my mid-2009 MacAir running the latest version of Yosemite.

The hardware test and diagnostics all depend on your model year. On my mid-2009, I have to insert the Applications Install DVD and then hit D. On yours, it might be different. Read the website and associated links for details relevant to your model.

I forgot one bit--sorry. Out of the test, I shut down and then boot up. At that point, nothing is changed. However, I then shut down and boot up and everything works, I have no idea why two reboots is needed for me. Still nothing on your second startup?

I have the same problem... and I don't know what to do. I hope that 10.10.2 will fix this annoying problem. My bluetooth is working, but no wireless. Ethernet at least works.

So for some reason, this same thing happens to me whenever I restart the computer, but to fix it I simply shut down instead of restart, and then when I turn it on manually it fixed this. But, this doesn't mean it fixes all my wifi problems. Or my spotlight problems. My wifi turns off randomly, even though my router is fine (I have 3 roommates and I never had problems until yosemite, then my wifi on the computer just shuts off) and now, for some reason my spotlight function doesn't work. It'll open, but whatever I type doesn't appear. Apple had better fix yosemite, I don't know how it's been this bad for this long without any acknowledgement.

I have the same problem here.

any luck with 10.10.2?

i had the same issue right after upgrading to 10.10.1, and it got fixed by reverting to 10.10 using the full install ISO loaded onto an external drive.

since then i restrained from upgrading again to 10.10.1 fearing that the same issue may resurface. i was hoping that the .2 update was fixing it, but apple seems to ignore this issue altogether...

I had the same issue... Intermittent access to WiFi, every now and again the dreaded gray WiFi signal with an "X' in the middle of it. I tried all the solutions listed here for software fixes. Made a Genius Bar appointment and the culprit was a jump cable. They initially replaced the airport card and the issue still persisted. The put my old airport card back in, changed the cable and all is good. The part is around $10.00 and there are videos that explain how to do it. Although it does require removing the display from the body. So do so at your own risk. It was $50.00 installed at the Apple store. This may be the resolution to some of the issue you all are seeing, it may not. But this was the resolution for me.