Hi folks. I decided to replace the aging default head unit.

• Sony XAV-1000
• Spiral Audio
• Fiber Optic + SWC Retention Interface: Allows for installation of an aftermarket radio while retaining use of the controls on the steering wheel that are lost when the factory radio is replaced. No programming required. The factory MOST fiber optic amplifier will be retained and 12V ignition will be provided by the SWC interface.
• 1 Fiber Optic Loop (I applied this to the NAV in the rear)
• 1 Fiber Optic Loop on order (going to use this in lieu of the cd changer, right now that is plugged in)

The unit worked fine upon initial startup, sound was good, CarPlay was nice. Upon turning the car off, the unit has not turned back on. I am unsure if the factory CANBUS is freaking out or what. I removed fuse 28 in front for some time, and reinserted, and the radio came back on with the key in ACC+. Since this works intermittently, I am not quite sure what the issue could be. I do seem to have this noise when the radio refuses to turn on https://mbworld.org/forums/c219/6714...out-noise.html . Unsure if there is something obvious to check during this odd behavior.

I suspect the 'on' signal is be interrupted or not being sent for some reason. And as I understand it, this comes from the canbus? I am going to eliminate the CD Changer still, not sure if that is causing issues or not.

To add more information here. I used a diagnostic tool and I do see that I get "D100 most master reports open ring" eventually. The radio does indeed work if I pull fuse 28 for a minute or two. Is it possible to have an open ring and have audio work at all?