After the first few trips with our new 23U replacing the Axxera radio went from a "someday" to a "right away" mod. I pulled out the Axxera and replaced it with a Pioneer, and also put in a dedicated monitor for the rear/side cameras at the same time.
The Axxera was powered by the coach battery, but I noticed it didn't keep the time when the battery disconnect switch was turned to store. Upon removing the Axxera I confirmed both the yellow "memory" wire and the red "switched power" wire both lost power when in store mode.
My original plan was to hook the yellow "memory" wire on the new Pioneer to a permanent chassis battery connection and keep the red "Switched" wire on the original connection from the coach battery. However I then realized that on the Pioneer head the main power draw is from the yellow wire and the red wire is essentially just a sense wire. This would have resulted in draining my chassis battery while listening to the radio in camp, so I just kept the original wiring for now.
I then tracked down the original yellow wire, which appears to have been connected (via an in-line fuse which is the small red colored wire in this picture) to the coach battery disconnect switch, except to the switched side instead of the battery side:
(Removing the in-line fuse confirmed that this wire did indeed provide power to the radio.)
Problem found! So I then switched this wire to the battery side of battery disconnect switch:
Easy fix... except it didn't fix anything. Turning the battery disconnect switch into store mode still causes the Pioneer radio to lose its time. Hmmm.
The obvious next step is to check the yellow "memory" wire in the back of the stereo to confirm its actually the same wire that I just switched. Pulling the dash trim out to access the radio is such a pain though it's going to be awhile.
I'm going to try and get electrical diagrams from Thor today to confirm the wiring.
Oh, and with the wire moved to the battery side of the disconnect switch I confirmed there is still no phantom load on the batteries when in store mode: