Dell does not repair monitors. We only exchange them after the fault has been replicated when testing on our validated Windows 10 operating system. Unfortunately, we can see here on the U3818DW validated operating system page that the proprietary Apple operating system and hardware were not tested/validated by Dell. For Dell to troubleshoot, you need to test/replicate the U3818DW USB Type-C issue on a Windows 10 PC.
Read through the U3818DW threads on the Apple Forum. If an applicable thread is not found, start a new thread out there. Perhaps the Apple users have some troubleshooting ideas and/or possible Apple proprietary cabling to purchase.
Power on my laptop is now up to 46% and I've connected my keyboard/mouse directly to my laptop. The problem is continuing.
Now I'm going to try connecting my power supply "brick" directly to my laptop to stop it from trying to draw power from the monitor itself.
After that, I'm going to ask my colleague (who is using the other U3818DW monitor with his MacBook Pro) to switch monitors with me for a time to see if he has the same problem. It might be an issue with the USB-C slots on my laptop.
USB-C -- such a convenience! But maybe not working all that well just yet?
I just now cross-posted to an Apple forum - here is the link:
I also posted a followup to the Apple forum.
Seems like the problem is related to low battery charge on my laptop. Once the battery charge rose above 79%, the problem stopped. (Big relief -- I don't want to stop using my fancy new monitor.)
I've been using Apple laptops for decades, and it's always been the case that if my laptop isn't connected to external power source, it can't easily drive an external display. Probably this is true for all laptops?
Sounds correct to me. When using Laptops with monitors and/or docks, I have always connected the Laptop AC power adapter.
We are using a lot of Chrome OS devices (Pixelbooks, Lenovo, Dell, Acer etc) with these monitors and we are seeing the exact same issue.
If the battery level of the device is below a certain percentage, the monitor connectivity is intermittent. As soon as the battery is above 85% or so, connectivity stabilizes.
While I understand you can simply plug in an external AC adapter, the whole reason we spend the extra money on these monitors is for the simplicity of the monitor being able to function also as a full dock.
I'm hoping a future firmware release will address this. The last release did a lot to make these monitors usable with non-Dell devices.