Friends, fellow MK4 DVD sufferers.

I have a beautiful e53 4.8is with the MKIV DVD nav and widescreen display.

It has a fault, maybe even several faults?

The unit is running the latest V32 firmware and UK maps with Perspective View & TMC. It uses the boot mounted BM53/4 Becker Radio with the Alpine Amplifier and NO DSP!!

All is good (I hear you say) what could possibly go wrong?

Well it has a mind of it's own and I am not sure what "it" is?

Problem: Driving along and for no obvious reason I will get a sharp & loud "bang" from the speakers, like a gunshot. This will usually be followed by the nav re-booting itself. This is seen by the display going off, restarting with the splash screen then returning to the nav/map view, as if nothing has happened. Sometimes it will repeat this process, several times. Other times, it will issue the loud bang but not re-boot.

Now here is the thing!! The bang happens regardless of whether the head unit/BM53 is on or off. If the orange light is out on the display it can still happen. The same is true as to what input source is selected, Radio, CD, Tape, Aux. It makes no difference. You are driving along and BOOM - Reboot.

Now. I recently had the BM53 repaired (it had no sound output at all). In doing so, I checked the boot for water ingress = none. I also ssprinked talc powder in the boot and washed the car several times with a hose to ensure no water ingress - none.

The radio checks out fine and works fine. I have removed the Aux lead and still get the problem.

I have no idea where to start looking here. As it re-boots the nav system is it likely to be the MKIV unit itself?

I have tried new firmware and also downgraded to v21 the upgraded to v32 to ensure that it is taking the firmware properly.

I have also switched off TMC. I read that this can overload the radio and nav causing re-boots? I still get the issue with TMC off.

Now here is the other thing. It sometimes does it when the car is stationary but with the engine on. So that would rule out, driving over a bump.

It causes no issue other than annoyance and pooping my pants when it goes bang during some nice piano concerto.

Oh. I recently rebuilt my compressor using the piston kit from bagpipingandy.com. This gave me a great opportunity to inspect the boot and all the wiring. No issues seen.

The car has a brand new battery. Some say that this should be coded to the car? Others say that is nonsense. It is 2006 4.8is which I believe is the N62 engine. From what I can see the battery is not on any intelligent charge although it does have a thin black wire running up the main live to the battery terminal? But the earth is a straight earth with no fancy stuff attached.

Please can you help me and my underpants here?