USB-C monitor keeps disconnecting and re-connecting

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Level 1

6 points

USB-C monitor keeps disconnecting and re-connecting

I keep having an issue where my usb-c monitor keeps connecting and reconnecting every minute or so while plugged and and extending displays. I am using a MacBook Pro 14.

I have already tried:

3 different usb-c monitors, all with the same issue
changing usb-c display cables
updated from MacOS Monterey to Ventura

Nothing has worked. Any guidance would be appreciated because it is quite annoying that usb-c external monitors just refuse to work with Apple MacBook pros for some reason.

MacBook Pro 14″, macOS 13.0

Posted on Oct 30, 2022 4:00 PM

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Answer 1

Top-ranking reply

MichaelDro Author

Level 1

6 points

Nov 2, 2022 5:07 PM in response to Grant Bennet-Alder

First, Really appreciate the response. Definitely makes sense logically. I do however have a couple follow ups to that:

Why is it possible that my windows laptop connects with no issues whereas my Mac won't? Wouldn't this data rate problem be one for both laptops then?

And another point, I used the cable that came in the box for this monitor on my last 2, I believe it was 6ft long approx. and the issue was still the same. Only now have I tried a new cable which happened to be 10ft. How could a 6ft cable that comes with the monitor not work either?

I will be trying a shorter cable though just to be sure and thanks for those links!

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Answer 2

Nov 2, 2022 5:37 PM in response to MichaelDro

The Mac sets the resolution to "best for display" based on sending a query to the display, essentially "what is your name and what are your capabilities?"

recent MacOS seems to be more capable of reading any errors received by the display, sent back across the secondary channel at low speed. More than an occasional error can cause a disconnect, and if the cables are not really good enough, that could be often.

PC sets whatever resolution, color depth, and refresh rate you say, and never looks back. ¿is it set for 10-bit color? 8-bit color is MUCH easier to attain.

Long cables are unlikely to be able to perform properly, unless they have repeaters inside the cable like this one (note the much higher price):

Apple Thunderbolt 4 Pro Cable (3 m) - $159.00

Cables 'shipped in the box' are often 'lowest bidder' cables -- good enough to keep you from returning the product, but maybe not much more.

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Answer 3

bruno75

Community Specialist

Nov 1, 2022 5:36 PM in response to MichaelDro

Hey there Michael,

You tried some great steps already, and we'd like to continue ruling out some other possible causes:

Is there an adapter that connects between the USB-C monitor and your Mac, is are they directly connected to each other?
Is there anything else connected to your Mac(besides the charging cable) when this occurs?
Are you using any USB-C hubs to connect to your Mac?
If these monitors worked in the past, when did the issue first start?
Have these monitors been tested with a different computer?

Cheers!

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Answer 4

MichaelDro Author

Level 1

6 points

Nov 2, 2022 1:30 PM in response to Grant Bennet-Alder

LG 34WP88C-B

using a 10ft usb cable.

When connecting to my windows machine though, this issue is non-existent so I don't think the cable is the issue in this case but could be wrong.

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Answer 5

MichaelDro Author

Level 1

6 points

Nov 2, 2022 1:34 PM in response to bruno75

No adapter, usbc from monitor directly to usbc port on MacBook Pro 14

Nothing else is connected to the Mac directly. My monitor has a usb a port that I connect a Logitech wireless keyboard/mouse combo into but otherwise nothing.

I guess technically the monitor is acting as a hub itself, but no external hubs are used

Issue started a short time after using the Mac. I would say I got a few days - a week of inconsistent use from all the monitors before the issue arose. This latest one started after maybe 2 days.

I have a windows laptop that I use for work on this monitor for upwards of 10 hours a day for the past 2 months. Not a single issue. Second day I ever used my MacBook on it it started the issue.

This makes me think it is a Mac specific issue because I have switched cables, monitors, and operating systems and the only constant is the Mac.

Any guidance from here would be appreciated!!!\

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Answer 6

Nov 2, 2022 5:01 PM in response to MichaelDro

That display is UWQHD 3440 by 1440, a very high data rate. Your USB-C cable Is far too long for reliable operation.

You need to switch to a much shorter USB-C cable rated for use with displays. For 10 bits/pixel, you need about 17.28G bits/sec Total transfer rate. A high speed USB-C 3.2 cable rated for 10 G bit/sec can use both sets of leads outbound most of the time and attain those speeds at shorter distances.

Monoprice Essentials USB Type-C to Type-C 3.1 Gen 2 Cable - 10Gbps, 5A, 30AWG, Black, 0.5m (1.6 ft)

Product # 27923 - $5.60

Monoprice Essentials USB Type-C to Type-C 3.1 Gen 2 Cable - 10Gbps, 5A, 30AWG, Black, 1m (3.3 ft)

Product # 24285 - $18.49

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Answer 7

Nov 1, 2022 6:10 PM in response to MichaelDro

what make&model displays?

At very high resolutions, the data rate gets close to the maximum possible switching speed for electronic devices. Cable lengths can be very important.

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Answer 8

MichaelDro Author

Level 1

6 points

Nov 2, 2022 5:38 PM in response to Grant Bennet-Alder

Appreciate the in depth response, super helpful!

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USB-C monitor keeps disconnecting and re-connecting

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