My wifi drops when I plug in an external monitor through the thunderbolt port

Another solution which works in my case (MBP15 2016, external monitor via non-original hdmi-typeC adapter) is to wrap cable with Kanthal A1 wire (ferritic iron-chromium-aluminium alloy).

Not sure why, but foil did not work in my case.

This was the only thing that worked for me also! Tin foil to the reduce. I have a brand new 15" 2016 MacBook Pro. Apple really needs to find a way to stop this from happening, having tin foil next to my nice new computer is not ideal.

Try this, go to system preferences then network preferences. Select Thunderbolt Ethernet and "make service inactive" (click sprocket icon at the bottom)

This improved my WiFi connection speed. My thought being that Thunderbolt is a multipurpose port also used for ethernet and may be taking priority when it is plugged into any device. If you are using WiFi Thunderbolt ethernet is obviously not needed.

I had this issue with a new MBP retina. I have two external Dell monitors hooked up to adapters that go to their DVI-D connectors. Each adapter takes up a Thunderbolt and a USB port, so it maxes them out. Having the adapters plugged into the MBP dropped the wifi by x10. I solved this by reading this thread: Macbook pro retina drops wifi when usb 3.0 stick connected

I moved the cables and the adapters as far away from the back hinge as I could. They had been about 4" away. The wifi went up to almost the same strength and throughput as when the adapters were not plugged in. Hope this helps.

Same problem. My setup:

1. MacBook Pro Retina
2. Mountain Lion
3. External monitor attached via Apple Thunderbolt-to-DVI adapter
4. Network connectivity available via wi-fi only

Consistently, I could not connect to wi-fi with the Thunderbolt cable attached but could with it detached. I changed the wi-fi settings on my Linksys router to use channel 1 instead of channel 6 and the problem disappeared.

Thanks to all of you who posted before me and helped me solve the problem quickly!

Same here!

• Macbook Air late 2010
• new LG 27" HDMI Monitor
• third party hdmi adapter

Instant drop from 50Mbit to 2Mbit when connected, physical proximity is NOT important. Macbook can be right next to monitor (connected to Windows PC) and still achieve 50Mbit, only when it it CONNECTED the speed drop occurs.

Tried swichting channels, doesn't work for me (best I can do on other channcels is 5-8Mbit).

Solutions:

• Swiching to 5Ghz! Works like a charm. (but not good for me since my external WiFi USB Stick on my PC does not support 5Ghz)
• Connecting to Monitor (if possible) via VGA. Worse display quality but full 50Mbit.

This gets more and more confusing! -.-

Mine was also fixed by changing to channel 1 (D-Link router was set to auto-select and was using channel 5). I'm NOT using thunderbolt.

My old configuration:

• MacBook 3,1 (that's right 2007!)
• Mini-DVI to DVI to Dell2001FP (lid not closed--spanned, not mirrored)

Wifi immediately stops working with external monitor connected with native 1600x1200 60Hz. Lowered to 1344x1008 60Hz, still does not work. Lowered to 1280x1024 75Hz and it works. Changed router to channel 1 and native resolution works! I'll repost if anything changes.

I now recall having this problem over a year ago but since others on the network were also having issues (not the case this time) I thought it was the router and replaced it. That solved the problem until a couple days ago. Glad I found this thread and will try the "aluminum hat" fix if it comes back!

I am experiencing the same problem on macbook air 13'' 2010 and macbook pro with retina display mid-2012 . When I plug external monitor to thunderbolt port through hdmi adapter, my wifi connection drops. OS X Lion on both.

I am getting this issue with a Macbook Pro retina with Lion. When I plug monitor into another computer the wifi is fine. As soon as I connect to thunderbolt the wifi instantly disconnects. It's as if the thunderbolt port is draining the power from the wifi interface.

I might add I have a 2nd monitor in the HDMI port which doesn't intefere with wifi.

There are tonnes of forums with these complaints out there. I have tried some of the advice, like changing wifi channels and buying an Apple made mini displayport adaptor without any success. And now I am wondering the same thing as raysian. If the problem is simple interference with the monitor why does my wifi work perfect when I am not plugged in but beside the monitor (the monitor is on not in sleep mode) yet instantly drops when I plug into the monitor? The problem seems to be very big as it is affecting many generations of macbooks.

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.

Not sure if Apple's interference statement is really valid as my old ThinkPad T60 shows no WiFi problems at all at the same time and same place.

Count me in for this one too...took me WAYYYY to long to make the conenction ( I have a new office and only use the big monitor at work). I've been complaining about the wifi at work for weeks. Today my mouse died, so I had to open it and and BOOM, blazing speed. ***. Channel Change didn't work....I'm bummed.

Hey. I actually found a solution to this. It's extremely weird and I called apple to talk to them about it but they had no idea what was going on. This isn't going to make any sense, but just try it. Lower your external monitors resolution.

I kid you not. I was having this same problem with my macbook pro "13 I bought two weeks ago. Plugged it into my external monitor and internet crapped out. Then I realized uplugging my monitor fixed the issue instantly. After doing some searching I found that lowering the resolution fixed it for one guy. My original resolution was 1400x1050, internet didn't work. I tried 1344x1008, internet didin't work. Went one lower to 1280x1024, boom, internet back to normal. I can switch between the resolutions and see it not working and then instantly working again at 1280x1024.

Hope this helps someone else.

Edit: I also found that if I change my wireless routers channel from 11 to 1, I could function at higher resolutions. Something else to try. I have no idea why that would be happening though.

I'm having the same issue with wifi dropping when a display is plugged in. My setup:

- 2012 MacBook Air (OSX 10.8.2)

- Apple Cinema Display

- Apple brand Thunderbolt-DVI connector

- Airport Extreme Base Station

Wifi works fine when the same Thunderbolt cable is plugged into our iMac.

Plug Thunderbolt into the MacBook air and it kills the wifi. Unplug Thunderbolt and wifi comes back.