Macbook wireless signal appearing and disappearing at random, wtf is going on?

May 9, 2009 2:16 AM

Mac, wireless, bizarre behaviour. I share a wireless connection with other people, and every two or three days the connection on my Macbook does this very odd thing.

Okay, so this is a bit of an odd one, with some strange wrinkles that may or may not matter. Here's the deal:

- I live in a small, close-knit community in South London. One of the guys here used to work for a local council as a flash developer, so his flat is wired for corporate grade broadband. Being the all-around great guy he is, he's daisy-chained a load of wireless routers together through the shared loft space of the building we live in, and for the princely sum of £20 a year, I get 8Mb (or better sometimes) broadband. I know, right?

- The router that I use, No 3, has had it's fair share of problems. It kept crashing or disappearing from our router lists (there are a good half dozen routers, some belonging to the communal system, some to individual flats). The guy who runs the system replaced this router with a new one, and gave us a USB stick with the new WPA key on it.

- I entered this WPA key on my Macbook, my wife's iBook G4 and my xBox 360. Both the iBook and the 360 now connect fine, rock solid connection with no problems.

- Here's where it gets weird. Everything worked fine on my Macbook for a few days, then one day I closed it to go and do something else. When I came back, I was still apparently connected, but couldn't get any pages to open. Then I noticed the wireless signal would appear, full bars, for 3 or 4 seconds, then disappear (no bars or one bar then no bars) for 5 or 6 seconds, then reappear. Pinging google.com or any other site through Terminal got a 'no internet connection' message.

- Here's where it get weirder. I've tried a bunch of things to fix this intermittent and incredibly irritating problem:
* Removing Router3 from my list in the Network Preference pane, then re-adding it
* Deleting my 'login' keychain to remove the WPA key, then re-adding it
* Trashing the preference file for Internet Connection

Sometimes, after doing all of these things and restarting, I'll get a strong connection back (usually 4 bars). Sometimes, it won't work. And sometimes, it seems not to work, but I close the laptop in annoyance and, when I come back to it the next morning, it's working fine.

This is driving me up the wall. I can't restart the router because I don't have physical or wireless access to it, and the fact that all the other internet-connected things in my house are working fine with it points to that not being the problem. I think I maybe have a corrupt or unneccessary keychain file somewhere that is pointing to the old WPA key for the previous router (there's a WPA key for Router3 in the 'System' keychain that I can't delete or otherwise remove).

What on earth is going on here?

posted by Happy Dave to computers & internet (13 comments total)

It sounds like you might have a Airport specific issue (bad AP card/loose connection) with your MacBook. How does the wireless connection work in other places?
posted by ShawnString at 3:48 AM on May 9

Not a clue, I've never tried it anywhere else but the house.
posted by Happy Dave at 4:08 AM on May 9

I'm not seeing this as a WEP issue, you're not indicating that you're getting messages about incorrect passwords. It sounds more like signal interference or, as mentioned, perhaps a problem with your macbook airport card.

The first thing I would do is test the macbook on another connection (can you get access to another router in your "chain of routers", or spend some time at a coffeeshop to see if you can maintain a connection. If you rule out the MacBook as the problem it narrows things down a bit.

You might also want to see if you get get the owner of the system to change the channel of the router and see if that helps..
posted by HuronBob at 4:17 AM on May 9

See my similar question from two years ago. Basically people settled on "Apple has problems with Airport cards and won't acknowledge it." This still happens to me with my Macbook -- and not just on my router at home.
posted by proj at 6:11 AM on May 9

I manage 250+ identical MacBooks for my faculty. About half a dozen of these have had the issue you're describing--strong signal, no IP (goes self-assigned), no ping, other identical equipment sitting right next to it have no issues, etc.

In these cases, we've fingered hardware as the culprit and have had Apple repair them. I've replaced the Airport card in one or two of these and it's resolved the issue. In other cases, Apple has swapped out the logic board. In one (and only one) case out of the approximately 10 that I've seen, has reinstalling the OS resolved the issue.

So, yes....there is historic precedent of problematic Airport cards that Apple won't acknowledge, as proj suggests, but my guess is that you either have a loose or bad/marginal Airport card. Taking off the top case to get to the card to re-seat it isn't that hard. iFixit.com has take apart instructions, if you wish. Your easier solution is to take your MacBook to the London Apple Store and ask them to look at the issue. Describe it exactly as you have here.
posted by mrbarrett.com at 6:24 AM on May 9

Hmm, don't want to reinstall if I can help it, so time to check my Applecare agreement and head into the Apple store.
posted by Happy Dave at 7:51 AM on May 9

The problem you're going to have is demonstrating this intermittent issue to the techs at the Apple Store. Be sure you tell them that it's intermittent and therefore harder to troubleshoot. It may help you have with you a list of things you've tried in troubleshooting the issue, and at the very least a detailed and accurate description of the problem. "Um, Airport no workie" isn't really enough.

Allow the tech to do an "Archive & Install" of your operating system, if they deem it necessary. This simply moves your old OS out of the way and installs a fresh one, retaining your User profile, 3rd-party Applications, and Network settings.
posted by mrbarrett.com at 8:47 AM on May 9

I just wanted to confirm that your "Trashing the preference file for Internet Connection" step included trashing the ENTIRE /Library/Preferences/SystemConfiguration folder. (And, as you mentioned, restarting.) This has resolved nuuuumerous bizarro networking issues for me in the past.
posted by trevyn at 9:52 AM on May 9

Go take the Macbook to a coffeehouse or someplace else that has wifi. If the same problem occurs, your Mac has a problem. The thing about trying a couple of other hotspots is that you can tell the tech that the problem occurs anywhere, which means it's probably an issue with the computer itself. We did this with my wife's Macbook. They put in a new Airport card, but the problem quickly returned. The next time they replaced the logic board and it's been working like a charm ever since.
posted by azpenguin at 3:44 PM on May 9

I will take my Mac for a wee walkabout (there's a few places hereabouts with wifi) and see if I can duplicate the issue. Thanks for the advice folks, and I'll report back when (and if) it's resolved.
posted by Happy Dave at 4:25 AM on May 10

There may be an update for OS X to 10.5.7 out soon. This is definitely an annoying issue.
posted by acro at 11:11 AM on May 10

I think I've fixed it.

I used the instructions on this page, recommended earlier in the thread, to crack open my MacBook and take a look at the connectors on my Airport card.

None of them appeared to be loose, but I popped them all off, gave them a clean, made sure they were back on very securely and closed the whole thing back up again. Warning - if your tolerance for tiny, tiny little screws is low, don't do this.

So far, it seems to have worked. Before, the weird connection errors were showing up after I closed my laptop. I've done it a dozen times now, switched the Airport card off and on, and it's reconnecting rock solid every time.

Hurrah!

I'll repost if it doesn't stay fixed, but thanks for all the help folks.
posted by Happy Dave at 3:04 PM on May 15

Further update. It seems to have been router-specific (although I don't think that reseating the wireless card did any harm). After a thorough reboot by the guy who manages our network, the signal is now rock-steady, returning from sleep or otherwise.

Thanks all for your answers and suggestions.
posted by Happy Dave at 1:21 AM on June 9