I have a MPB 2015 13" MBP with High Sierra. I bought a ViewSonic VP3881 monitor. Monitor works flawless. (Except for a documented feature of sound control access from keyboard not working.)

But for some reason the wifi is being VERY spotty. I've had the monitor for 2 weeks now and I can't find an obvious pattern, except that it looses connection with the wifi on an irregular basis, while at the same time I have an older MacMini 2014 (El Capitain) on the same wifi, that does NOT drop the connection. Sometimes when rebooting it picks up the wifi, sometimes not even after reboot. Unplugging the monitor seem to make the wifi came back every time though.

Why would an external monitor interject with wifi?

This seem like a hardware problem, so I'm more or less forced to accept the situation, but hoping that there might be a checkbox somewhere I need to set to fix it?


External monitors can emit signals that interfere with WiFi signals. This is commonly due to insufficient shielding within the monitor. I would complain to ViewSonic - they might know about a design deficiency for this particular monitor, and have a solution or rebate at hand.

In order to try and fix this yourself, the most common way to solve this is simply to move your WiFi to a different set of frequencies, and hope that the monitor is not producing interference with that set of frequencies. It is usually hard for home users to shield the monitor properly without it being an ugly hack.

In essence you would need to access the settings on your WiFi access point and move it to a different channel. For example if you're using channel 11 now, try using channel 6 instead. You might need a few tries to find a sweet spot.

You can also switch from 2.4 Ghz WiFi to 5 Ghz WiFi if you have that available.

  • Here’s Apple support page about this issue. – IconDaemon Mar 8 '18 at 12:28
  • I presume that's not the case by this simple test : I have the laptop next to the monitor, but not connected & have functioning wireless service. I then connect to monitor, whereby the wifi stops working, until Chromes gives up and says I'm not connected to the internet. I then unplup the monitor and the laptop then picks up the wifi again. During this whole operation I have not physically moved the computer at all. So I presume it's not signal emission interference. My MacMini is just a few feet away and has never had the problem at all, hence my thought it's High Sierra... – Michael Mar 10 '18 at 20:33
  • When your laptop is not connected, the monitor isn’t emitting signals. Try the suggested channel change - it takes only a few minutes to be sure – jksoegaard Mar 10 '18 at 23:50
  • Called ViewSonic support and they had no known issues about this monitor regarding wifi interfearrance. So I changed the cables : Original cable: Mini DislpayPort Male (MBP) ==> DisplayPort Male (Monitor). New cable : HDMI (MBP) ==> HDMI (Monitor). Had a weird red spots buzzing for a few minutes then fine. Initially Wifi works. Giving it a few days to see if this holds. – Michael Mar 12 '18 at 15:46

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