A3 rear sound loss

[wingdiver]

Hi

This is a first post by a new user so let's hope it's OK.

Here goes...

I have a 3 door 2001 A3 with a standard (non Bose) sound system with a sub in the nearside boot locker.

I have a problem with losing all of the rear sound. It started as an intermittent fault but has progress to being the norm. There is sometimes a faint clicking from the rear nearside (sub area).

I have had a search around and found a few possible solutions:

Wiring fault - like the wires have parted somewhere and are causing an intermittent loss of sound

Amp fault - connections or possibly dry solder joints

Speaker fault - sounds the most likely - one of the rear speakers or the sub is 'shorting' and this causes some kind of overload protection to cut in and turn off the amp

Has anyone had this fault and cured it? Can you let me know what to check, where to look, advice about removal of panels may be needed too.

If the amp is shot, is it better/cheaper to replace with an aftermarket one.

Thanks

W

 

[AndyMac]

Hi Wing, welcome to the forum.
The A3 non Bose has the rear speakers and sub driven off the tiny amp inside the tupperware sub. I doubt very much that there is any sort of overload protection on the amp as it really is basic. If you can hear clicking it is likely to be the relay in the amp. So could be a number of things.
Dodgy connection on the plug/socket, the red one on the outside of the sub.
Poor remote on from the HU.
Faulty amp.
It's not easy to replace the amp with aftermarket as you'd never be able to get a tri-mode one small enough, so you'd have to mount it somewhere else and run new power to it.
If you have a multimeter then you could check that 14v is reaching the amp supply and remote on, and check the ground is good. Pin outs below:

 

[wingdiver]

Thanks for the info and pic Andy

I will dig out the old multimeter and give it a shot.

If the power supplies/ground are OK, is it likely that one faulty rear speaker could stop all three functioning?

If not, is there anything I can test at the head unit out to check it isn't a front to rear cable issue?

Are there any wiring diagrams available for the audio system anywhere?

Cheers

Wingdiver

 

[wingdiver]

Andy

Sound like you have the A3 systems sussed.

I will do some testing with the meter tonight to see if I can find problems with the ground/remote on/positive.

Couple of daft questions -

What is the 'screen' on the multi plug diagram?
I assume the '+12v' will be the standard battery voltage but will the 'remote on' be the same or is it changed somewhere along the way?
Are there any other checks I can do at the plug?

One final thing, there was an Alpine multichanger and ICD lead installed relatively recently. The problem existed before this so I am assuming this was not the cause but, in my current state of paranoia, I am wondering if this may have increased the problem.

That said, when the lead was connected to the rear of the head unit I noticed that a split multiblock was used. However, since the install, the head unit has been taken out again and the security of the blocks has been rechecked and found to be stable. Hopefully all will be revealed when I have run the tests.

Thanks for your offer of a pre-demolition job test.

If I start to spend too much time on this, I may be down to see you for an amp/sub/box fitting.

Cheers again

Wingdiver

 

[AndyMac]

The screen is the protective earthed/grounded shield around the low level pre-out signal feeding the amp. This is only something to check if you are getting engine interference from the rears, should be same as earth/ground.
12v & remote on should be the same (12v or 14v with the engine running).
It could be that there is a slight short or a duff connection on the remote on, which is causing the voltage to drop to less than 12v, this would cause the amps relay to switch on & off repeatedly if it was borderline.
The CD changer can't effect what you are experiencing, but you're absolutely right to be paranoid as Audi car radio tends to do that to you (so many little intricacies).

Is there anything else that could be running off the remote on output of the head unit?
Some bodger could have wired it in to power a hands free kit/mp3 player or something it is not up to the job of doing.

 

[AndyMac]

If you can unscrew the speaker without removing the sub, this will give you access to the amp (as it is screwed to the back of the speaker, but I don't think you'll have enough room to manoevour the speaker/amp out of the cubbyhole.
I have a sub and amp all ready to go if you fancy an upgrade.
Here's a photo of the OEM sub/amp out of the box so you can see what you're dealing with.

 

[wingdiver]

Andy

What sort of money are we talking of for the upgraded gear?

Is it worth doing anything else at the same time?

What sort of time frame are you looking at?

W

 

[AndyMac]

£325 installed, that includes the sub enclosure, JL sub, Alpine V12 4 channel amp (mounted behind the rear speaker panel), wiring, power cabling etc and installation (4 hours).
The only worthwhile adition is upgraded front speakers but this doesn't have to be done at the same time. You can upgrade the rears but it will have little effect on the sound in the front.
Timeframe is up to you, whenever you can get down to Southampton, can be a weekday if it helps.

 

[wingdiver]

Andy

Quick reply so you don't think your quote has scared me off.

Unfortunately, I have been unable to do anything else as my Father has been taken into hospital.

Once things are sorted, I will have another look at things and, if I get no joy, I would like to take you up on your offer of sorting this.

Would you want to arrange this 'off forum'?

If so, what's the best way.

Cheers

Wingdiver

 

[AndyMac]

Sorry to hear that about your Dad, hope he's ok.
Just send me a PM when you're ready or mail at andrew.macgregor@hp.com.