MacBook Pro Retina Display with External Monitor and WiFi

My problem is similar. I have a MacBook Pro 2011 running Mountain Lion and a 23" Acer Monitor. I have WiFi when connected through Thunderbolt port, yet it is extremely slow. 1.5 Mbs download when connect to monitor, 10.5 when just using the laptop normally. Interestingly, upload speeds are not affected by the Thunderbolt monitor.

Seems to be an OS bug, though. Nothing seems to work.

Any info would be greatly appreciated, however.

UPDATE: I have solved my problem, and want to share this info in the event it helps anyone.

When my MBP is closed (clamshell) and connected to external monitor through thunderbolt port, i get slow Wifi. If I open the laptop, however, Wifi is normal. I suppose this isn't technically a solution, but rather more of a work around. However, the end result is my stuff works as it should now.

Hopefully, Apple will fix this weird bug soon.

FYI, I had some trouble seeing everything on my display with the MBP open. To solve this, I went into display settings on the MBP and clicked "Mirror Displays."

Good luck!

I am experiencing something similar.

MacBook Pro Retina. Connect to external monitor via the Thunderbolt DVI adapter. Wifi speeds drop from 10 mbps to under 1 mbps.

Wifi works just fine on iPad and other devices.

Disconnect the TB DVI Adapter and the Wifi speed immediately jumps back to normal. No reboot necessary. At least that made it easy to determine the source of the problem.

Am going to try why savvypavvy did and run the monitor through HDMI > DVI Adapter tomorrow and see what happens. Pretty lame if it is a shielding issue.

I am having a similar problem. I am not using Thunderbolt however, just a HDMI to VGA connector. When clamshell mode and external monitor is being used. SUPER slow WiFi. When I disconnect the external monitor and use it as per normal; works fine. Very strange.

Colin

I was having this same problem.

Macbook Wifi worked great when standing alone.

When connecting to my Dell external monitor via Miniport or HDM > DVI adapter, it immediately cut out. Unplugged it, and it worked great.

Tried using an HDMI > DVI adapter with extra long cord to see if there was an issue with poorly shielded adapters (cord moved the adapter part far away from the mac itself). Worked great when on my lap, but again the Wifi hung when I put it on the desk.

At that point, I figured it wasn't the adapter shielding, or a software problem. It was from the monitor itself.

Solution was to change the channel on my router. It was set to automatic. I manually cycled through the different channels until I found one that avoided the same frequency as the monitor. Problem solved.

Also heard that baby monitors can be the source of interference.

The fix for me was to leave the laptop open when Thunderbolt display is plugged in. This works fine. Kind of ***** you can't close the computer, but it's a workaround until they fix this.

I had the same problem conecting an old HP2035 monitor. I cheked wich WIFI chanel my router was on (7) and changed it to 13. and voila the monitor works fine on a thunderbolt to PCI conector and the WIFI is back to its full speed. I don't think its a connector sheilding issue but simple monitor interference with chanel 7.

On the Retina ones, has anyone tried both Thunderbolt ports? I had an issue with using an external monitor not waking up when it was plugged into the port closest to the power connection. Just wondering if this issue follows that same pattern...

Very similar issue here:

Brand new MBP Retina + DELL 2007 FP monitor, connected via a ~ 2 year old Apple Mini DisplayPort to DVI adapter. Extremely slow WiFi traffic or even problems connecting to WiFi. No matter which of the two Thunderbolt ports, no matter wether the laptop is open or closed.

Everything is working fine as soon as the DELL monitor gets unplugged.

Yeah, I'd try resetting the WiFi frequency. I put mine at 11 and the problems disappeared.

Not sure why the MacBook Pro is more sensitive to the interference than my PC was, but it's certainly the case.

Pretty sure I eliminated unshielded cabling or software / hardware problems as the issue.

I also went into my router settings, and changed the channel to 11, and it solved the problem. I have a mid-2012 Retina MBP running Mountain Lion 10.8.2, and as an artist I depend on my Wacom Cintiq to make a living. I was extremely frustrated upon seeing my wifi connectivity disappear when I plugged into either of the thunderbolt plugs. Hope this helps!

So glad to see that this worked. 🙂 I have a Cintiq too and it was frustrating to not be able to go online while working.

Please, try to add a couple of aluminium foils between the keyboard and the screen before closing you MBP.

I konw, it seems crazy, but for me it works!!