Monitor glitches on USB-C, but not on HDMI

Question

Monitor glitches on USB-C, but not on HDMI

Andy 0

I have a widescreen LG monitor that we use with 4 different laptops, some without HDMI port. I bought a USB-C to HDMI cable, which worked fine with different ThinkPad laptops, on Linux and on Windows.

Now I have a new Dell Latitude 7340 from work, and it glitches on both its USB-C ports:

It recognises the monitor correctly when plugged, shows the according animation and moves windows to the external monitor. However, the monitor itself shows a “no signal” message, and then switches off.

It does work on the laptop’s HDMI port, but it’s a pain to use the HDMI cable, it takes more space on the desk.

So I tried changing the only available option, the refresh rate, but it doesn’t have any effect.

The recognised monitor details seem to be the same on HDMI or USB-C. I reset drivers several times already.

Thanks for help!

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2 answers

Your answer

Answer 1

Andy 0

Hi and thanks for looking into this.

The cable must be a passive one, it has a simple USB-C plug on one end, and an HDMI one on the other.
Similar to this one: https://www.amazon.fr/Acer-C%C3%A2ble-USB-C-vers-HDMI/dp/B0GJ5TYDYH/ref=sr_1_1_sspa?__mk_fr_FR=%C3%85M%C3%85%C5%BD%C3%95%C3%91&crid=1JGC2BSV2RYGS&dib=eyJ2IjoiMSJ9.GW6IYNNYa-veeAP3dZcGrCMhrZQUJ77F6zQ7phMOSs2E96xyp1oTl2-CJgaykpTl26nj1NDFz3YgwY4wWbV0GtTJ8UHGWO-Jh73Y3-jEB5frEcqb4GlGN74wkZaH3ybxwDhkA4Em7L1JkJvuP_QxfhQvORKngm4QpnTlWpfGKn91oONEniis-B3UxL3HCioAILrJSAH5rduUurll9T5auJbeeNFMWKwuqHxYitaNMyZ9E1AMHZEJDP_LHi1cF_o9yMaQENrW5ZojaSgvcGC5XwBelsBUYJJRY1jq_FEScSI.8euNZ8EohSzJ5bEhkbdAnkwlQA7n6-QulmUilrKf9Y0&dib_tag=se&keywords=hdmi%2Busb-c&qid=1784714698&s=electronics&sprefix=hdmi%2Busb-c%2Celectronics%2C180&sr=1-1-spons&aref=3KysIh9trk&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1And the issue occurs on both USB ports, both when plugged to AC power and on battery.

Emma1-N 10,135 Reputation points Microsoft External Staff Moderator

2026-07-23T07:25:34.3333333+00:00
Hello Andy,

Thank you for response. Please check the step:

Check the USB-C display mode reported by Windows

Open Settings > System > Display > Advanced display

Select the LG monitor when connected through USB-C

Note the resolution and refresh rate being negotiated

Force a lower resolution and refresh rate

Set the monitor to 1920×1080

Set refresh rate to 60 Hz

Disconnect and reconnect the USB-C cable

Install the latest Dell graphics and Thunderbolt drivers

Run Dell Command Update

Install all available BIOS, graphics, Thunderbolt, and USB-C firmware updates
Andy 0 Reputation points

2026-07-23T08:18:19.26+00:00
Thanks for the instructions.

I had checked the negotiated resolution and refresh rate, and they looked OK. 60 Hz was not an option, but 59.97 was. I had tried to lower it, to no avail, and the same with the resolution.

I just made sure to recheck in the order you mention, disconnecting and reconnecting the cable. There is no difference, it’s the same result.
The monitor wakes up every time I plug the cable (no matter the resolution), but stays black and then goes back to sleep.

When I first encountered the issue, I tried manually installing graphics drivers, and BIOS has been updated twice since then. There are no dedicated Thunderbolt drivers on the Dell website for Win11. I guess they are integrated into some other chipset drivers. However, everything is up to date.
Emma1-N 10,135 Reputation points Microsoft External Staff Moderator

2026-07-24T08:04:27.5+00:00
Hello Andy,

Please try the step:

In-place upgrade is a process wherein it will upgrade the device to the latest version and repair many issues without deleting any files. Usually, it is used to repair corrupted system files, apps, and even incompatible drivers on the system.

Go to Windows 11 website: Download Windows 11

Under Download Windows 11 Disk Image (ISO) select Windows 11 (multi-edition ISO)

Once done downloading the ISO, kindly right-click on ISO then click Mount> then Click Setup.exe

You may be prompted by User Account Control. If so, click on Yes.

In the Install Windows 11 dialog, click Next.

Setup will check your PC and show a license agreement. Click on Accept in the license terms dialog.

Wait for the setup program to check for the available free space.

On the Ready to install page, make sure Keep personal files and apps has been checked.

Then click Install and just follow the prompt.

Windows 11 will restart your device several times and lead you to the lock screen. Depending on the options you set, it will keep all your files, apps, and user accounts.
Andy 0 Reputation points

2026-07-24T09:59:44.04+00:00

Thank you Emma for the suggestion.

My taptop is a corporate machine, and I’m certain that I don’t have the rights necessary to run a full system repair. Maybe IT services can do that during my holidays, I will ask.
Emma1-N 10,135 Reputation points Microsoft External Staff Moderator

2026-07-25T07:58:06.84+00:00

Hello Andy,

When you have a chance, try it out and let me know the results.

Answer 2

Welcome Andy,

I understand how frustrating it can be when your LG monitor works correctly through HDMI on your Dell Latitude 7340, but when using a USB-C to HDMI cable, Windows detects the monitor while the monitor itself reports "No Signal" and turns off.

Before proceeding, could you please clarify:

Is the USB-C to HDMI cable a passive cable or an active adapter/cable?
Does the issue occur on both USB-C ports when the laptop is connected to AC power and when running on battery?

I look forward to your reply so we can continue working together to address the issue.