Stereo cutting out

Aj1 · Post by **Aj1** » Sun Mar 25, 2012 6:15 pm

It doesn't matter what I'm listening to (ie radio, cd changer, aux, cd head unit) it will just cut out,
It started a few months ago every now and then when going round a corner or under hard acceleration.
But now it's pretty much every time I drive the car, its mainly when pulling away in first (fast and slow). It also cuts out if I change settings or pretty much anything electrical related. I can sometimes get it back by pulling both electric window controls, it's almost like any surge or drop in power with mess with it.

I originally thought it might be a loose connector or wire but I've been though and checked all I can see (amp included) then thought it could be the aux I fitted so removed that yesterday but that's not helped. I've evening taken the amp out and checked for dry joints on the main bord but it all looked fine.

I'm now at a loose end as to what could be wrong

Aj1 · Post by **Aj1** » Sun Mar 25, 2012 8:22 pm

spareone3 · Post by **spareone3** » Tue Mar 27, 2012 7:57 am

What type of headunit?
Doesthe display reman on during the "outages"
Is it a soft off/resume, like a "mute" or can you hear a crack/click/interference sound like a poor connection.
Could it be going into Telephone Mute? Maybe another owner had a phone kit installed, or maybe you have something similar fitted?

Aj1 · Post by **Aj1** » Wed Apr 04, 2012 7:31 pm

I've got the business nav head unit, the screen stays on as if nothing's changed and theres no noise when it cuts out it just drops and the dsc option is unselectable. I've never noticed any remains of Bluetooth kit behind or anywhere else.

I've also tried giving the dash a thump to see if it was a loose connection but it just made the cd skip lol.
It's just very random now, i'll drive to the shop and it'll cut out as soon as I set off but then work fine on the way home

bcworkz · Post by **bcworkz** » Thu Apr 05, 2012 1:29 am

Are you running heat through the dash vents? I managed to trip some sort of thermal cut-out doing this on cold top-down drives with the volume up (both heat and audio

). Hasn't done it since I found the windscreen vents were just as marginally effective as the dash vents.

Bobby. Bodgit · Post by **Bobby. Bodgit** » Wed Jan 11, 2017 12:16 am

Anyone got a solution to this? My car does exactly the same thing. Sound cuts out randomly, but often when pulling away. (touching the accelerator does it). Flicking the electric windows when engine is idling will bring sound back.

vester86 · Post by **vester86** » Thu Jan 12, 2017 12:07 pm

check your speaker wiring for some bare pieces. could be it's making short circuit of circuit to chassis when the isolation is off at some point. when installing my new audio i had a short circuit at some point & the radio didn't give any sound at all, however everything else would operate normal.

Edit: doors Will Be prime suspect as sound comes back when flipping the Windows. Weird probleem though

DMC63 · Post by **DMC63** » Thu Jan 12, 2017 12:35 pm

Eeewww! Time to pull the insides of the out and check the wiring and head-unit. Unusual for the wiring to be a problem unless it's been tampered with or modified. Head units like all electronic devices are prone to conking out over time. Hope this is an easy fix for you.

Bobby. Bodgit · Post by **Bobby. Bodgit** » Wed Jan 18, 2017 1:46 pm

It not only the windows. I can turn the amp on and off with the heater blower ! - Its clearly some low voltage issue.
I connected INPA and checked fault codes and nothing stored in the amp ( when there is sound); however, when the amp drops out, I lose access to the amp via INPA. This implies that the amp is being switched off as I can't communicate with it ( dsp functions disappear at this point too).
The BMW WDS information talks about a wakeup line from the HU to the amp and refers to 8v trigger - there isn't anything marked as trigger on the wiring diagram but I do know that the k-bus runs at 8 volts.
So, I am assuming that the wakeup line and the k-bus are the same, and also losing comms to the amp points me in this direction - the fact that there are no faults stored is another key fact as turning the amp off with the k-bus is perfectly normal and therefore you don't log a fault.
I've had the amp apart and re-soldered the k-line connections as far as I could follow them. Put it all back together and fault is still there

.
Connectors look clean at the amp and there is no sign of water damage anywhere

I'm beginning to doubt that its a problem with the amp at all and perhaps the k-line is broken/intermittent somewhere between the HU and the Amp. It can't be a short circuit on the k-bus as all the other ECUS on the bus would go beserk.

note that I have also rewired the supply directly to the battery ( via a fuse of course), so I don't think battery voltage is an issue ( could still be ground)

(worst case scenario is that the previous poster of this issue never got it fixed and I have actually bought the same car !)

Anything wrong with my logic ?

I think I need to run a wire from the HU to the amp connecting both k-bus lines together..

rapidroy · Post by **rapidroy** » Tue Jan 24, 2017 1:24 am

my car was doing it also . i fixed it by holding down the music note 2+ sec and that got me to a menu that i changed the speed of the sound going up and down as the noise in the car goes up and down. I slowed it down to 2

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Bobby. Bodgit · Post by **Bobby. Bodgit** » Tue Jan 24, 2017 3:54 pm

I'll give that a shot, but can the speed related volume really turn the amp off ?

I got an oscilloscope on the car at the weekend to see if the k-bus line and supply line dropped so far that the amp would turn off.

I connected two channels, one to the input voltage to the amp, and the other to the k-bus and used the headlamp main beam to turn the amp on and off ( I know, saves reaching for the volume control right ?)

The scope I used was able to do on the fly calculations, so I set it up to subtract the k-bus from the supply - if the difference goes negative then the amp should turn off.

I was surprised at how low the voltage dropped when turning the main beam on. I always thought the voltage regulator could control to within a volt, voltage dropped by over 2 volts and the amp turned off as the supply voltage recovered.

summary so far is that the k-bus is fine , no need to run a separate line, but new voltage regulator is in the post - I will post further results when I swap the regulator.

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Bobby. Bodgit · Post by **Bobby. Bodgit** » Tue Jan 24, 2017 7:26 pm

The speed related volume control trick didn't work. Amp cut out about half way home. Had me fooled for a bit, but amp failed as usual.

Bobby. Bodgit · Post by **Bobby. Bodgit** » Mon Feb 06, 2017 9:52 am

voltage regulator swapped at the weekend. Apparently more stable voltages, but stereo still cuts out

Bobby. Bodgit · Post by **Bobby. Bodgit** » Sat Feb 11, 2017 10:03 pm

System now fixed. Second hand amp from ebay has worked.
Of minor interest is that watching the voltmeter on the dashboard is very stable and doesn't drop on pull-away.
Use test 19 and press lock off. Then test 9

jabber · Post by **jabber** » Sat Feb 11, 2017 10:33 pm

Glad you got it fixed

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