E51 No sound with engine running?

KFC

Member
E51 Owner
#1
Hi guys, as per the title. My van has stopped making any sound through the sound system as soon as the engine is turned on. I've got an after market hu fitted, which I installed myself and had been working fab until just recently.
I've removed the hu and checked all cables and all seems fine, so I assumed the unit was at fault. I've just tried a replacement and am getting exactly the same thing.
Acc only.. Works
Ignition on.. Works
Engine on.. No sound but unit playing as it should!
Any ideas before I spend a fortune on an auto sparky?
Thanks in advance guys.
 

MrRob_in

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#2
So 12v from harness stops on engine on? Or it’s still there going to unit (otherwise hu would stop) but hu stops outputting sound?

Is there a mute (trigger) wire to hu that is being grounded or powered at engine on?
 

MrRob_in

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#3
ie multi meter on all the wires hu is connected to and what’s different at engine on?
 

KFC

Member
E51 Owner
#4
I've taped off any none required wires when I fitted the initial hu, the replacement doesn't have that function. But I'll the meter test, and see what happens!
Thank you
 

MrRob_in

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#5
There is a command link between hu and nav module to control sound between nav phone tv etc perhaps there is a missing link? But I don’t recall others having this issue. I certainly didn’t in my old e51 but I’ve kept current one standard to avoid issues like this ;)
 

MrRob_in

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#7
It’s a odd (and interesting) problem. The only thing I can think that should change is voltage as alternator kicks in. But why would that kill sound but allow HU to still operate?
 

KFC

Member
E51 Owner
#8
Thought I'd post an update to this ongoing issue. After messing about this afternoon and proving and poking things, with the engine running I found that if shut the tail gate, sound could be heard for a few seconds then stop. Ive proceeded like a demented valet assistant to open and close doors to see this did the same thing. On trying the drivers side rear door the sound returned in an on off Manor. However only when the door it's self moved and not by just wriggling the harness at the bottom! In frustration I slapped the door card and sound could be heard! Meh!
I've now run out of day light so I shall concentrate my efforts I that area tomorrow. Any findings I shall duly share!
 

MrRob_in

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#9
Wow! Very odd. I wonder what the bad connection or short is affecting?
 

MrChops

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#11
These are the threads that I read and just have to know what the solution was. Damn my curious nature! Good luck in your search.
 

Karl

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E50 Owner
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E50 Expert
#14
This sounds like a really odd problem.

In all honesty, sounds like you need an auto electrician.

Have you checked the earth to the head unit? This only difference between ignition in ON position and engine running is the voltage output which goes from 12.5v to 14v with engine running (due to alternator). There are no other electrics that are "turned on" when the engine is running.

With the engine running the key sits in the ON position. I imagine, when you are opening or closing the door, you are drawing more current (lights on/soft close) which mite cause a momentary drop of voltage as power goes to the lights and soft close, allowing the head unit to output sound, but quickly reverts back to 14v which then stops it.

Of it could be vice versa and the alternator is not putting out enough voltage. But somehow opening a door increases it momentarily.

Other than that, I'm all out of ideas. Definitely an earth issue. If it's not the head unit, see if you can find any of the standard earthing points in the car (there will be loads under and behind the dash. Maybe also create your own earth strap from the battery to the chassis. If making your own earth strap from the battery works, you could look to get an earthing kit.
 

KFC

Member
E51 Owner
#16
I think I may have solved it? Apologies for not posting for a while but life came before fixing my beastie!
It would appear that the fault was being caused by a door speaker being fitted upside down (by me). It seems that over time the terminals on the speakers had dropped slightly and were making contact with reinforcement bar in the door but only she was running probably due to the vibration of the engine?
I've been running about in her today (with the door card still off, just in case!) and I haven't had a drop out once since rotating the speaker through 180 degrees. So fingers crossed, I'll let you lovely people know there is any further problems. Thanks for your help and input.
 

Karl

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#17
Thanks for the update mate. Happens to the best of us.

My rear speaker kept tripping out because I lost the cover for the crossover, and the electrical components were shorting against the body. I stuffed it in a sandwich bag and boom, job done :joy: