[Jplath]

Hi all, I have a 2014 BMW 535i m sport. The sound stopped working I checked the fuses replaced the amplifier and still no sound. My car sat for a week while we were on vacation, I started the car and I had sound, sterio worked, warning chimes worked and I had communication to my cluster again. Everything worked perfectly for a week then the sterio started cutting out now it stopped working again I'm absolutely stumped. Could this be the head unit itself? Also my nav does work but doesn't show up in the cluster anymore.

[Morfy]

On the F10/F11 cars, the “no sound + no cluster communication” issue is almost always tied to the head unit (CIC/NBT) or the MOST fiber optic loop, not the amp itself. Since you already replaced the amp and the problem went away temporarily, it’s unlikely the amp was the root cause.

A few things to check:
– MOST bus loop – the audio system (head unit, amp, combox, etc.) all talk over fiber optics. If one module drops, it can break the loop and kill sound + cluster info.
– Head unit (CIC/NBT) – these do fail with age/heat. The fact your nav still works but doesn’t project to the cluster hints the HU isn’t communicating properly.
– Water/moisture – check the trunk area around the amp/Combox for water intrusion. Even slight corrosion on the fiber connectors or grounds can cause intermittent cut-outs.
– Battery/voltage – low voltage after sitting can trigger these gremlins. If your battery is original, have it tested. Weak batteries can make the HU or amp glitch until fully charged.

Since it came back after sitting and then failed again, I’d lean toward the head unit itself starting to fail or a bad connection in the MOST loop. Best next step is to run an ISTA scan — it’ll show which MOST module drops off when the audio cuts.

So yeah, could be the HU — but before you buy one, check for water in the trunk, clean/inspect the fiber connectors, and make sure your battery is healthy.