# BOSE wiring identification and advise please!



## ProjectMick (Sep 29, 2015)

Hi all.

Have grabbed myself a second hand head unit and proceeded to read the 4 million threads on Bose adapters half/full ignitions etc etc and have managed to get to a point where I think I am almost ready to go (not really, still totally confused lol!!!).

Have a loom adapter and have hooked up what I think makes logical sense.

So I started by connecting the Blue wire from the head unit to the Blue and White wire coming from the red connector
(Note: this isn't actually connected with sellotape!! It is temporary for the photo!)










Next:
Plugged in Blue and White to Blue and White.
Repinned the Yellow to Yellow wire (marked constant).
Black to Black.
Then finally there was a spare Grey wire with a connector on which I have currently plugged the Red switched live into.



















So now before I plug everything in, I wanted to know if anyone can identify the wires coming from the head unit loom.

I assume that the Large Brown wire is Earth and the Red/White is constant live, but what about the other three?










If one of the wires isn't a switched live (my car is a 51 plate so I am hoping that it "might" be??) then I can disconnect the switched live and run it to the bus bar.

Finally, does the Blue Ariel booster wire also splice into the blue wire coming off of the head unit?

Any other observations welcome as I'm not really sure how it all hooks up!!

Thanks in advance!


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## pcbbc (Sep 4, 2009)

ProjectMick said:


> If one of the wires isn't a switched live (my car is a 51 plate so I am hoping that it "might" be??) then I can disconnect the switched live and run it to the bus bar.


If the car has CAN (did you get station info on the cluster with old headunit?) then you will *NOT* have switched live.
If the car was pre-CAN, then I can't say. But I presume must have had switched live, as could not use CAN to determine ignition on?

Post a screen shot of the wiring diagram which is located on the top of your OEM head unit (assuming that is what you are replacing). This is the easiest way to identify what wires are what in the harness.

edit: FYI:
KL is the abbreviation for 'klemme' which is the German term for connector / connection.

KL15 is ignition switch position #2 (on)
KL30 is battery positive, hot at all times
KL31 is battery negative, connected all the time
KL50 is ignition position #3 (start)
KLR means ignition switch position #1 (accessory)

Edit again. Looks very much like this Chrous II Bose setup to me:









So as you identified:
Permanent live (red/white top - back left)
Ground (Brown - back right)
Plus:
K-Line for diagnostics (white? - middle left)
Bose ground pin (brown? - front left)
Alarm ground pin (brown? - front right)

So look like you will need switched live from bus bar under steering wheel. Drop lower dash panel for access.


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## ProjectMick (Sep 29, 2015)

Thanks - that was really helpful!

It is Can Bus so will run a switched live for now and then maybe put a relay in at a later date.

The Blue and White wire is the remote turn on lead which seems to be connecting to the Bose ground on that diagram (I'll just leave it there as it was the default pin position)

So really just need to double check if the rest of the wiring is ok now.

Now does anyone know if the power antenna lead (plain Blue) should be connected to the Blue and White wire as in the first pic? If so, do I also splice in the plain Blue lead from the Ariel booster at the same point?

Other than that Should be good to go I hope.


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## pcbbc (Sep 4, 2009)

ProjectMick said:


> The Blue and White wire is the remote turn on lead which seems to be connecting to the Bose ground on that diagram (I'll just leave it there as it was the default pin position)


So blue/white goes hot (12V) when new headunit is ON? i.e. it is the headunits switched live output?
If so *!!! Do not connect to BOSE pin in wiring harness !!!*
BOSE pin in wiring harness is a permanent ground, and so you have just created a dead short.
Instead connect BOSE pin in wiring harness to permanent ground (or leave n/c as it's grounded anyway).

Switched output from your new stereo should go to connector pin that was connected to the "_/+_" pin (second from right on the middle row of the bottom connector). That is the switched live output from the Chorus II that powers on the BOSE amp.



> Now does anyone know if the power antenna lead (plain Blue) should be connected to the Blue and White wire as in the first pic?


But the 8N Roadster didn't have a power antenna, did it? So this shouldn't be connected anywhere...
What was the original source of the blue/white wire (in the old harness) that you are connecting to?



> If so, do I also splice in the plain Blue lead from the Ariel booster at the same point?


Yep, if you have an aerial boster that needs to be +12v when the radio is on, so connecting to power antenna output is correct.

It would be much easier if you could post pin-outs/wiring diagrams (for both old stereo and new stereo), and say what connections you have made. Pictures of wires are okay, but often hard to see exactly what has been wired where. However just mentioning wires by colour is next to meaningless, I'm afraid.


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## ProjectMick (Sep 29, 2015)

Thanks again.

Not sure why the wiring harness is made like that though - it is supposed to be plug and play so I would have assumed it would be correct!

No worries - I'll pop outside tomorrow when it's light and have a proper look.

I'll also grab some photos of the wiring diagrams as well - just to compare.


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## ProjectMick (Sep 29, 2015)

Ok

Have just removed the Blue and white wire from the connector. So just the constant 12v and ground wires connected now.

This leaves me with two wires - the Plain Blue (power antenna) and Blue/White (Remote turn on) coming from the head unit to connect up.

There is a Blue/White wire coming off of the Red connector - I believe it is the plain Blue wire people connect up but not 100% sure.

If anyone knows please chime in, if not I'll go and grab some wiring diagrams from the old head unit in the morning.


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## desertstorm (Apr 25, 2017)

Not sure if this helps. It's the wiring diagram for a Bose equipped TT.

View attachment BOSE radio wiring.pdf


Karl


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## ProjectMick (Sep 29, 2015)

Thanks for that it's appreciated - I can't pretend I understand it properly though ha ha ha!

I think I am almost there now - was just thrown by the extra wires in the plug that connected to the car and ended up overcomplicating it! I assumed they all had to connect to something but it seems they aren't needed.

Just removed them and will shoot off to Halfords tomorrow to get some connectors and a fuse for the switched live. Then I will hopefully get time to hook it up and test it out.


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## pcbbc (Sep 4, 2009)

If you have BOSE, then you need the remote turn on from the new headunit to go to the BOSE power on pin in the red connector that I pointed you to earlier. Otherwise amp will not power up, and so you won't get any output.
But yes, not everything has to be connected. Power antenna, for example, not needed as standard TT (even Roadster) didn't have a power aerial.

And, no, the Audi wiring diagrams don't make much sense to me either.... 
When I do this I just cross reference between old and new headunit pinouts.


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## ProjectMick (Sep 29, 2015)

I think it is all sorted - quick test earlier seems to be working fine.

I'll get out and fit it properly tomorrow I hope - I'll also take some photos and post up.

Like many before, I think I just overthought/overcomplicated it!!!

Thanks for the help guys!


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## TTT2004 (Jun 4, 2018)

Hello fellow TT owners! I recently bought my first mk 1 TT coupe 1.8T 225PS (2004). Loving it so far but now wanting to make a couple of little changes (new wheels and stereo upgrade).

I've done various stereo changes over the years but this is one is causing me a little grief! I bought a new JVC head unit and the Connects2 CT53-AU03 as I have a BOSE amplified system at present with Chorus tape deck and 6 CD changer in the back (which all currently works ok).

I've added a new switched wire from the bus bar from under the dash and spliced to ignition wire on Connects2 harness. Also switched over the red and yellow bullets on the jvc harness. Stereo received power and turns on and tunes in etc. all good there.

Now to the amp!! The Connects2 harness has 2 blue leads with female and male bullets labelled Amp On and Remote Signal (12V when ignition on). I've connected these together and the amp seems to switch on, albeit quite noisily with a high pitched noise that then stops after a number of seconds and then a low hum/white noise, but no music etc.

I tried dis connecting the two blues bullets and just connecting the blue/white coming out of the the JVC head unit that goes to antenna amp blue on Connects2 harness to the Amp On blue on Comnects2 harness but same result. Also tried connecting Amp On blue wire on Connects2 to the switched live and again same result!! No sound 

If I turn stereo up full I get a very small amount of sound out of front right when Amp is connected on ?? I've retested old Chorus to check amp and speakers all still work and they do.

I will post up a picture of the sticker on Chorus headunit when I work out how to, but I can see that the red large Connects2 plug connects with the __/ + __ and Com on the middle row and the RR (right rear) and LR (left rear) on the top and bottom row.

I've seen a lot of threads on here and other sites that talk about the BOSE system only amplifying the Front right and Front left signal. Could this be my problem?

Any other comments on set up please before I lose the will to live!!

Many thanks


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## pcbbc (Sep 4, 2009)

TTT2004 said:


> If I turn stereo up full I get a very small amount of sound out of front right when Amp is connected on ?? I've retested old Chorus to check amp and speakers all still work and they do.
> 
> I will post up a picture of the sticker on Chorus headunit when I work out how to, but I can see that the red large Connects2 plug connects with the __/ + __ and Com on the middle row and the RR (right rear) and LR (left rear) on the top and bottom row.
> 
> I've seen a lot of threads on here and other sites that talk about the BOSE system only amplifying the Front right and Front left signal. Could this be my problem?


If you have BOSE in a Coupé then yes, because only line out RF and LF line outputs drive the amp and the RR and LR line outputs, as well as the LF and RF speaker outputs do nothing.

Seems to me you likely have a wiring harness from a non-BOSE system, where front speakers are driven directly from head unit (LF and RF in middle plug) and rears are driver through separate amp (from RF And LF in bottom plug)? Either that or a Roadster BOSE system where rear line outputs are used to drive the sub channel.

From the hum/crosstalk you are getting from the amp currently, sounds to me like front line inputs are not connected and so floating; so probably the former.


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## pcbbc (Sep 4, 2009)

CT53-AU03 is for non-BOSE. It has 3 plugs:
black = power/CAN/etc
maroon = amplified front speakers
red = amp remote and line out (powers and drives rear amp in non-BOSE systems)

CT53-AU04 is for BOSE. It has 2 plugs:
black = power/CAN/etc
red = amp remote and line out (drives all speakers via amp in BOSE systems from front channel line out only)

Seems to me very much like you have the wrong harness adapter (non-BOSE) for what you say is a BOSE car.
You can either send it back and get the correct adapter, which I think is CT53-AU04, or you could move the RR and LR pins over to the RF and LF pins on the red plug - at least then you should get some output, although it will be driven from the rear line output so your front/rear fade will be "round the wrong way". You could of course correct for that at the other end by re-pinning the mini-ISO as well. Not that front/rear fade makes any difference in a BOSE Coupé as only the front channels are used.


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## TTT2004 (Jun 4, 2018)

pcbbc said:


> CT53-AU03 is for non-BOSE. It has 3 plugs:
> black = power/CAN/etc
> maroon = amplified front speakers
> red = amp remote and line out (powers and drives rear amp in non-BOSE systems)
> ...


You are very right indeed, thanks!!

I do have the "full BOSE" as people call it and the harness I purchased is incorrect.

Halfords attempted to flog me the PC9-408 for £40 but I said no thanks and instead switched the pins in the red plug (not easy!!). All works fine. Getting stick on dab aerial and mic in on passenger and driver A pillars was a bit of a faff, as was getting all wiring etc and stereo hu in to recess but all in now, working fine and sounds great. TT radio cover even shuts 

Thanks again for advice. Not going to lose sleep over fade as it works fine and car is so small that rear to front fade not really an issue!


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## pcbbc (Sep 4, 2009)

TTT2004 said:


> Thanks again for advice. Not going to lose sleep over fade as it works fine and car is so small that rear to front fade not really an issue!


No problem.

Front to rear fade never going to work in a Coupé with BOSE, anyway. It is disabled via coding on the OEM headunit because the stock amp only uses the front channels to drive both front and rears and disregards rear channel line outputs. The only way to get it to work is virtually a complete rewire and bypassing the BOSE amp for either front or rears, or both.

Depending on how much pin swapping you did, the only issue here will be that full fade to front might result in no output, and fade to rear in full volume (i.e. you are using rear line outs to drive BOSE amp). The "correct" adapter cable would have use the front line outs, and then fade to front gives 100% volume and rear 0%. So no loss in functionality, just possibly a reverse of the front/rear fade action - which is totally useless in the BOSE coupé setup anyway.


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## tsutta (Aug 17, 2020)

Any thoughts how faceplate is connected to radio.

My original TT Radio died. I purchased radio that I thought would be same but has wider faceplate. Both Radios are Concert II. The replaced radio works but just has wider faceplate.

I see no ribbons going from radio to faceplate.


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