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Mike, Mac Medic
Category: Mac
Satisfied Customers: 8624
Experience:  Over 20 years IT experience with Apple computers in publishing, marketing and design.
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I have a MacBook Air about a year old running El Capitan.

Customer Question

I have a MacBook Air about a year old running El Capitan. For the last week or so several problems having been happening:
1) The Wifi usually displays about 12 networks - of these I have the passwords for, and can usually connect to about 6 of these - this list will suddenly truncate to about 4 networks including 2 I can connect to, but the system says it can't connect to any of these.
2) The Wifi starts to cycle fairly regularly between Wifi on and Searching for networks - the system won't let me connect during this time.
3) On Switch on the Wifi connects to one of my networks, but if I try to connect to another known network, the system won't allow me to.
4)The wifi Just drops the connection and won't pick it up again.
All of these things can happen in the same session, and their incidence is getting worse!
Submitted: 1 month ago.
Category: Mac
Expert:  Mr.Med replied 1 month ago.

Hi, I'm Welcome to JustAnswer. I'm reviewing your question now, and will post back with your reply ASAP.

Expert:  Mr.Med replied 1 month ago.

When did this start, How often does the connection drop?

Customer: replied 1 month ago.
I first noticed it about a week ago although it might have been doing it intermittently for longer than that. It is now doing it every two or three minutes, hence this conversation is taking place on my iPhone!
Customer: replied 1 month ago.
I would prefer if you connected to my MacBook, but you can't because of the WiFi problem!
Customer: replied 1 month ago.
I am going to have to leave for an appointment in about 20 minutes - presumably we can resume this conversation later?
Expert:  Mr.Med replied 1 month ago.

Please ty to delete your existing Wi-Fi Preferences in El Capitan OS to Start Fresh :

  1. Turn off Wi-Fi from the menu item in the upper right corner of OS X
  2. Go to the Finder (the smiley face icon in the Dock), and hit Command+Shift+G to bring up the Go To Folder command, choose the following path exactly: /Library/Preferences/SystemConfiguration/
  3. Hit return to go to that folder, then locate and select the following files:
  • NetworkInterfaces.plist
  • preferences.plist

5.Move all of these files into the trash (you can also make a backup of those files)

6.Reboot the Mac

7.Turn on Wi-Fi from the wireless network menu again

Let me know the results

Thank you

Expert:  Mr.Med replied 1 month ago.

Sure, let me know when you are available


Expert:  Mr.Med replied 1 month ago.

Has everything worked out please?

Customer: replied 1 month ago.
I'm not going to be able to try this until tomorrow afternoon - I live in Spain - I will let you know the results then!
Expert:  Mr.Med replied 1 month ago.

Ok, I hope it works out.


Customer: replied 29 days ago.
I had some work that I had to do off line, which I did but also answered messages/emails etc as they came in. Perversely, my Mac has been stable since i switched it on and therefore j don't want to try your solution until it starts to be unstable again, so that I can see it has worked. I will keepin contact with you to let you know how it goes once the Mac goes unstable again and I try removing the oreference files you suggest.
Expert:  Mr.Med replied 29 days ago.

I'm glad to know that, If you have a moment please rate my answer by clicking on one of the stars, positive rating are appreciated, if the problem persists please reply back to me and i will gladly continue to help.

Note : Only Rate answer after you are 100% Satisfied. Please do not rate an answer as poor or bad service, if you are not satisfied.

Thank you

Expert:  mary-cssm replied 26 days ago.
Dear Customer,
We received your customer service inquiry, however, we are unable to respond to you because we do not have your email address. Please contact customer support at***@******.*** and provide us with your email address and a link to this question page so that we can help you.
Thank you, ***** Support Team.
Customer: replied 25 days ago.
Okay, my Nacbook started to play up again, so I tried to do what you said, but when I click on Finder and hit Command+Shift+G, it doesn't bring up a 'Go To Folder'! My OS C El Capitan version is 10.11.6
Expert:  Mike replied 25 days ago.

Just click on the first icon in the Dock the face the Finder then Go at the top of your screen to Go to Folder and put in


then hit Return. In the folder that opens find SystemConfiguration and drag all the items except

to the Trash then restart the computer and immediately hold the Shift key until you see the Apple logo. This will activate Safe boot and it will check the drive for errors among other things. It may take longer to boot and you may see a progress bar during part of the process. If it starts up OK… login then restart the normal way from the Apple Menu. You will have to reconnect to your WiFi. Let me know after.

Customer: replied 25 days ago.
Before I continue, there is one folder and 13 files in that folder - please confirm I should delete all except the boot list file - the previous expert said only to delete 5 files!
Expert:  Mike replied 25 days ago.

Yes correct

Customer: replied 25 days ago.
That appears to be okay, but as the problem appeared to have rectified itself a couple of times before, I will wait 24 Hurd before rating the answer. Do I take it that the next time I switch on it will start normally? What is the implication of those 13 files and 2 folders being missing from the configuration folder? Is there anything else I need to do?
Expert:  Mike replied 25 days ago.

No nothing else you need to do, let me know

Customer: replied 25 days ago.
That did not work. The wifi is on and showing currently 4 networks 3 of which I should be able to join but it won't join any of them.
Expert:  Mike replied 25 days ago.

1. Shut down the computer.

2. Plug in the power adapter to a power source, connecting it to the Mac if its not already connected.

3. On the built-in keyboard, press the (left side) Shift-Control-Option keys and the power button at the same time, if it starts up you held the power button before the other keys, try again.

4. Release all the keys and the power button at the same time.

5. Press the power button to turn on the computer.

6. Press and hold the Command-Option-P-R keys before the gray screen appears.

7. Hold the keys down until the computer restarts again at least twice.

8. Release the keys.

Customer: replied 25 days ago.
I haven't done that yet but will do so after I pass the following information. After 10 minutes the system suddenly connected to one of the available networks of which there are now 9 showing, ; of which I can connect to - I am currently connected to the Internet via one of these. Do I still carry out the procedure you detailed?
Expert:  Mike replied 25 days ago.

It won't hurt

Customer: replied 25 days ago.
Done that - it's started up and awaits Password ***** what should I do?
Expert:  Mike replied 25 days ago.

It sounds like you may be back in Safe mode it should not ask for passord unless you have it set to do that at every strartup, just login and restart the normal way.

Customer: replied 25 days ago.
it is set to ask for password ***** time. Have logged in and it looks okay again, but as before I will wait 24 hours before confirming answer worked. Thanjs
Expert:  Mike replied 25 days ago.

No problem. If you are satisfied, please kindly provide an OK or Above Rating when you are sure - so I get paid. Also please note we get paid the same no matter how long it takes to solve your issue, so bonuses are GREATLY appreciated. Keep in mind you can always come back to this page at any time regarding this question. Thanks!!

Customer: replied 24 days ago.
Unfortunately, although it worked most of the day the problem has re-emerged. Currently the Eifi states that it is looking for networks, is however apparently connected to one of my Wifi networks (it is ticked) and is displaying the normal Wifi sign with 4 bars, but the message in the centre of the screen is 'not connected to the Internet'. My main problem now is that I am setting off in my Motorhome on a trip from Dpain to Denmark, and as a backup am going to take my old Windows 7 laptop, but still want to resolve this problem. However I will be reliant on Wifi hotspots and this iPhone or the laptop to communicate with you. I await your response on what to try next.
Customer: replied 24 days ago.
I'm not sure why you keep changing the expert that is dealing with this issue - doesn't this involve a loss of continuity in resolving this?
Expert:  Mike replied 24 days ago.

It may be a hardware issue.

Reboot into the Recovery HD by choosing the ‘Apple‘ menu > Restart, then hold down the ‘Command’ + R’ keys on the keyboard during the start up process. If you can't get to that menu just hold the power button for 10 seconds until it shuts down. Then start it up again holding those keys. When you see the Apple Logo you can let go.

When the machine boots you may have to choose your language then you will see the OS X Utilities screen. Select the Disk Utility and then Continue. Then in Disk Utility select Macintosh HD in the left column (if there are two with that name or it is named something else choose the first indented item) and then on the right select the First Aid tab then select Run. If that is ok restart and upgrade to Sierra 10.12:

Customer: replied 24 days ago.
Before I do that, is the following information of any use. Before you answered I carried out your previous instructions re restarting when plugged into the power supply after holding down the shift/control/option/power etc, and the Mac has connected to Wifi again okay - died that change your advice?
Expert:  Mike replied 24 days ago.

No you did that before didn't you?

Customer: replied 24 days ago.
I did and it was okay for most of the day - I just wanted you to be award that I had done it again since last messaging you. I will try your new procedure in the morning before I set off in the Motorhome. Thanks
Expert:  Mike replied 24 days ago.

OK there is no need to do it again once it is reset. If it continues to have erratic WiFi connectivity after upgrading I would say you have some kind of hardware failure maybe only a loose antenna but you would need to have it looked at.