Wireless issues when plugging into Mac display

I have noticed that no matter where I am in the house, my Macbook Pro works with my Airport just fine. But when I plug the laptop into a 24" display, my wireless signal does one of two things: it drops a connection, going from full strength to nothing and back again, bouncing back and forth in a slow rhythm, or it will give me a huge drop in strength. Anybody have any idea why this is? Your help is greatly appreciated.

MacBook Pro 4,1, Mac OS X (10.5.6)

Posted on May 5, 2009 8:02 PM

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30 replies

May 9, 2009 2:09 PM in response to DaddyPaycheck

Thanks for the quick response and warm welcome. I apologize for not getting back right away; university projects have a stranglehold on my life.

I have an Apple Cinema Display 23" that I purchased in 2008. I do have the monitor and book plugged into the same outlet now, but I have replicated the issue with separate outlets. I was concerned about power, because I noticed that the book has to be plugged in to appear on the cinema display.

And when you referenced interference, such as in the "audio chain," I got a little lost—could you help me to understand this concept a little better?

Again, thank you very much for your time and assistance. I should be a little more timely now.

Best regards,
poidogproductions

May 27, 2009 8:29 AM in response to poidogproductions

Just to let you know I have basically the same experience with my MBP and a 20" HP external display. As soon as I connect the display to the MBP my Airport connection is either broken or is slow and intermittent. I'm connecting to an Airport Extreme Base Station. I figure it is interference from the display although the problem only appears after making the physical DVI connection.

Jun 18, 2009 2:02 AM in response to poidogproductions

Man, I thought it was just me. I've just recently started experiencing the same problem. Airport works fine on MBP 15" until I plug in DVI and then network connection appears to restart, connect, but not establish a connection. Unplug DVI and I'm fine. This is a recent development. All was working fine until the past two weeks or so.

Have had several things happen within a short span of each other, so my temptation was to suspect one of them - dropped my MBP, recently upgraded OS and firmware, had to re-setup my network after lightning took out main router, just re-hooked up Sharp displays after putting in new multimedia furniture. Ugh. Plus, seems like I'm always updating some software. But here's what's weirder, my secondary MBP works fine on both wireless and DVI. Because I don't use it as much, I don't make all of the same changes. So I still suspect something has changed with my primary MBP to cause this.

Jul 7, 2009 10:55 PM in response to sportscarma

I'm having essentially the same problem with a brand-new 13" MacBook Pro unibody.

Wireless works fine when the mini-DisplayPort-to-DVI connector is not plugged in, even when the external Dell monitor is turned on.

When I plug in the mDP/DVI connector, wireless stops working, even though the signal-strength indicator in the menu bar remains at full, and even though I'm holding the computer several feet away from the external monitor.

Also, my old black 13" MacBook's wireless works fine when connected to the same external monitor, using the same DVI cable (without the mDP/DVI connector, of course).

Thus, as far as I can tell, it's the mDP/DVI connector itself (or its presence in the MacBook's mDP port) that's causing the problem.

Very frustrating. Anyone have any ideas on how to resolve this?

Jul 8, 2009 2:02 PM in response to poidogproductions

I have also been having this problem. The internet is sometimes usable through the wireless connection when I have the DisplayPort adapter pluged in but it is very unreliable - either incredibly slow or just refusing to connect to sites. At first I thought it might just be a problem with something causing wireless interference but I eventually worked out that the problems were only occuring when the DisplayPort adapter was being used.

Mar 28, 2010 11:57 PM in response to dysteleologist

Glad to come across this thread (comfort in numbers!), since I was going crazy trying to figure out why my wireless connection kept dropping.

I'm using a relatively new MBP 13" (bought in summer 2009) and hooking it up to an external Apple 23" HD cinema display. Whenever I connect it to the monitor (via mini DVI adapter), the connection to my wireless signal either cuts out completely or the speeds are incredibly slow. By simply unplugging the monitor from the computer, speeds and connectivity return to normal.

Did anyone ever find a solution for this?

Message was edited by: drolnitzky

Message was edited by: drolnitzky

Apr 24, 2010 10:06 AM in response to drolnitzky

I too have confirmed that my wireless connection issues are caused by connecting to a 24" Apple Cinema Display. I connect with a MacBook 4,1 via an Altona DVI to Mini DisplayPort converter—not sure whether that's relevant. But if the monitor is connected, the MacBook struggles with the Internet. If the monitor is not connected, the MacBook connects and stays connected beautifully. When the monitor is connected, I will see full bars (as someone previously said), but running a ping even to my router sometimes shows 20% packet loss and very widely varied times, from 35ms up to 7000ms, even within one set of 5 pings. Yet even more strangely, sometimes when I'm connected to the monitor, though the connection may struggle to become established, once it's established it sometimes runs great, with full speed and no outages. Sleeping the computer and re-awaking almost inevitable leads to droppage though. So it's a very peculiar problem with many different patterns of manifestation.

Jul 12, 2010 3:10 AM in response to poidogproductions

Hi All!

Same problem here... I was going nuts! Windows can connect... Linux can connect... MBP could not. Unplugged my external monitor (connected via DVI) and wireless worked again. Strangely enough, it does not seem to work with my home wireless router, but using a different wireless router works fine? Very, very weird... I tried switching channels on it, but it did not seem to help.

Any help would be greatly appreciated!

Aug 23, 2010 5:18 AM in response to poidogproductions

I've been having this exact same problem for the past week, before that my Macbook Pro (2010) has been working fine in the exact same setting. It took me a few hours of googling to realise it may have something to do with my monitor which led me to this forum, and then after researching a bit more I realised my problem was because my Macbook Pro was closed (i.e. the lid was closed and I was using my monitor as an external display). Once i opened the lid back up and while it was still connected to my monitor, the download speeds increased 4-fold. I'm not sure if your problems might be the same as mine, as many of you didn't say whether you were using the monitor as a mirror or extension, but I'm so glad I've finally figured out the problem to my wireless issues so hope it helps you all too!

Sep 12, 2010 3:36 AM in response to poidogproductions

I also discovered that I have this issue today. Closing the lid is not the problem, as I keep it open while the external monitor is connected. Also, simply having the external monitor on without it being connected to the MacBook does not cause the problem either (I tried with another PC connected to the monitor). It is definitely happening just when I connect the external monitor to the MacBook.

However, since I read in some blog that switching channels might help, I just tried that, and the first result seem very promising (I switched from channel 11 to channel 5). It might be too early to cheer, but for the time being, the problem seems to have disappeared completely.

It did not occur to me to change the channel before, because the network strength indicator is always at 100%...

Sep 21, 2010 6:46 PM in response to poidogproductions

I also have the same issue, specifically similar to that of DimBimbleby, since I am using my MacBook (2008) connected to one of the Apple 24" LED Displays via an Altona converter in the mini-DVI port. The laptop works excellently when not plugged into the display, as do my DVD player (streaming Netflix) and my AppleTV (will never figure out why I bought that) - as soon as the monitor is plugged in, the internet is either extremely sluggish or does not work at all. It took me a bit to figure out that it was only after the display is connected (moved both things all around the house of course). Does anyone at all have ANY idea how to fix it or improve it?? It's really frustrating and I certainly did not pay all that $$ for the display for it not to work with internet. I recently sold an older style 20" ACD Monitor which never had a single issue working with the internet. I have a Linksys Wireless-N router which is not the greatest ever but works well with everything else. Please help!!!!!

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Wireless issues when plugging into Mac display

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