How To: Build a PnP harness to connect an amplifier/Bluetooth to any VW stereo

[mclovin]

When I bought my car I knew that I wanted to retrofit a VW RNS-510, but as I’m a bit of an audiophile I wanted to add an external amplifier and higher quality speakers for improved sound quality. I searched the Internet for a solution but the only real option I found was to add a Blaupunkt THA 475 PnP with a Blaupunkt VW OEM harness. This is fine, but it is an expensive solution and I must admit, I am not a big fan of Blaupunkt amplifiers, for the money there are much better quality amplifiers on the market so I looked into a way of adding an “off-the-shelf” amplifier of my choice to my system without having to cut any wires in the car’s original wiring harness.

As it turns out, this isn’t actually that difficult to do, I have now got my stereo set up and working beautifully using a plug-and-play harness that I built myself, as I know a lot of other people want to do something similar, I have put together this guide to building a fitting your own PnP audio harness for an external amplifier:


You will need the following items:

1.   Autoleads SOT-976 VW Harness for Bluetooth (£10-£15)
http://caraudiosecurity.com/shop/product/products_id/11957/referer/rc_googleproduct.html

2.   RCA Car 4 Channel Line Output Converter with Remote Output (£10-£40)
http://www.caraudiodirect.co.uk/celsus-lc7-four-channel-converter.html
or
http://shop.ebay.co.uk/?_from=R40&_trksid=p3692.m38.l1313&_nkw=RCA+Car+4+Channel+Line+Level+Converter+with+Remote+Out&_sacat=See-All-Categories

3.   Some assorted bits and bobs such as electrical connectors/soldering iron/heat shrink/harness tape etc.

Please note: If you have an MDI interface (VW iPod kit) you could use the harness that came with that kit instead of the Autoleads SOT-976 as the basis of your PnP harness, I do not have an MDI interface fitted which is why I have used the Autoleads SOT-976 as the basis of my PnP harness.

Don’t worry if you have a Bluetooth module installed (or are planning to install one) as this can also be integrated into this harness and I have included instructions on how to do this.


Step 1 – Modifying the Autoleads SOT-976 harness

The Autoleads SOT-976 is designed to be used with a  3rd party Bliuetooth kit (such as a Parrot unit) which is really handy as it lends itself very well for use with a line output converter, it looks like this:



The first thing to do is to cut the female speaker output ISO connector block off from the male Quadlock connector, like so:



Don’t cut it too short as you will want to re-use that ISO connector later on.


Step 2 – Connecting the Line Output Converter to speaker outputs

There are a few different types of Line Output converters (or LOC) on the market, here are two examples:

PAC OEM-2 (£38):


Chinese made unit available on eBay (about £10)


I purchased both units for the purposes of creating this, the PAC unit is more expensive but gives you a lot more options when it comes to how your output the signal, it is also quite well constructed but I found it a little bulky for this type of application. The generic Chinese made unit is smaller and a lot cheaper, the good news is that it’s well made, works brilliantly and it is cheap to buy. However, expect to wait at least a month for it to be delivered from Hong Kong, mine took forever to arrive! Anyway, I chose to construct my harness using the Chinese made LOC as you will see in the following photos, but you could use any type of LOC as the principle is the same, just make sure it has 4 channels and a remote output cable.

The first step is to separate out the speaker input cables from the power cables, I did this using a little bit of harness tape just to get the power cables out of the way whilst I worked with the speaker input cables.

Now all you have to do is to connect the speaker input cables on the LOC to the speaker output cables that you cut earlier on the male Quadlock of the Autoleads  SOT-976. The speaker input cables on the LOC will be labled, so just use the following pin diagram to work out which of the speaker cables coming out of the male Quadlock need to be connected to the corresponding speaker input cables on the LOC.



You only need to worry about connector block “1” as labled on the above diagram, the output pins are as follows:

1 –  Rear right loudspeaker, positive
2 –  Front right loudspeaker, positive
3 –  Front left loudspeaker, positive
4 –  Rear left loudspeaker, positive
5 –  Rear right loudspeaker, negative
6 –  Front right loudspeaker, negative
7 –  Front left loudspeaker, negative
8 –  Rear left loudspeaker, negative

Remember that diagram is drawn as you would be looking at the back of the stereo, or from the side of the male Quadlock that has all of the cables coming out of it.

You can use crimp connectors to connect these cables up, but I have chosen to solder my cables together and finish with heatshrink for a higher quality and longer lasting connection. Once done, your harness will look like this:



You can see that I’ve tucked the three power cables from the LOC behind the male Quadlock for the purposes of this photo only, so far they have not been connected to anything, so let’s get those connected now.

To do this, you will need to cut the black power ISO conector away from the female Quadlock connector on your harness, cut this pretty short, leaving as much free cable coming out of the female Quadlock as possible as you are not going to re-use the power ISO connector. Once done, your harness will look like this:



Step 3 – Connecting the Line Output Converter to power outputs

***NOTE: Skip this step if you are going to use this harness with a Bluetooth Module***

Okay, the last thing to do is to connect up the power cables and then you can wrap up the harness with harness tape and fit it to the car, it’s pretty simple, all you need to do is to connect the power input cable from the LOC to the yellow cable from the female Quadlock and the ground connector cable from the LOC to the black cable from the female Quadlock which will look something like this:



Now you just need to wrap the cables with some good quality harness tape and add a bullet connector to the remote output cable with a crimp tool and you have a finished PnP harness.

If you were wondering why I suggested keeping hold of the female speaker ISO connector that you cut off earlier on, it is so you can connect it up to the end of the speaker cables coming from your amplifier, if you route this through to behind the stereo then you simply need to connect it to the male speaker ISO connector on your wiring harness meaning that you do not have to cut or modify any of the standard speaker cables in your car – Simple! When it comes to fitting it’ll look something like this (please excuse the iPhone camera photo):



Assuming you have already fitted your amplifier (Pretty straightforward so I won’t detail that here) you are now ready fit your new PnP harness, so simply disconnect the Quadlock connector behind your stereo and fit your new PnP harness between the stereo and the car’s Quadlock connector. You then need to connect everything else up behind your stereo (RCA output, speaker cables and amplifier remote power output), refit the stereo and you’re done. Once connected, you will need to recode your stereo via VCDS/VAG-COM as the speaker out put needs to be changed from “output stage power 26 dB” to “output stage line-out 12 dB”, there is a good guide on how to do this here:

http://www.my-gti.com/1411/volkswagen-rns-510-coding-when-installing-with-a-factory-amplifier

Once recoded, you are ready to enjoy your standard VW headunit with any off-the-shelf car amplifier that you have fitted, for me this is the perfect solution as I have retained a completely standard looking interior but now have far superior sound reproduction thanks to the hidden amplifier. I would also recommend changing the standard speakers for higher quality units as well, but that is not something I’m going to include in this guide. Now, sit back and enjoy your new improved car stereo, I think you’ll agree it was worth all the hard work you’ve put into this!


Step 4 – Adding a Bluetooth module to your PnP harness

If, like me, you have a Bluetooth module such as the VW Premium, Skoda or Fiscon units that are widely available, you can easily extend the functionality of this harness allowing it to be used with these kits so you don’t need to modify the standard wiring harness in your car or fiddle about with VW repair wires and multiple connector blocks. Assuming you skipped Step 3 it’s pretty straightforward.

Note: I have the Skoda Bluetooth module fitted to my car that came with a harness, I don’t know if this differs to the harnesses supplied with the VW Premium unit or the Fiscon unit, but please note that this guide refers to the harness supplied by VRStu with the Skoda Bluetooth modules.

First thing you will notice on your Bluetooth harness is that it also needs to connect to a +12V and a ground connector, which means you can join the appropriate cables from your Bluetooth harness to the +12V and Ground input cables coming out of the LOC, you then need to connect these up to the yellow and black cables coming out of the female Quadlock connector, the Yellow cable is +12V and the Black cable is ground.

Secondly, you will need to connect up to the CAN Hi and CAN Low connectors on the Quadlock, this means cutting into a couple of cables on your harness. Going back to the VW Stereo output pin diagram, you need to focus on connector block “2” this time:



The output pins are as follows:

9 –  CAN bus, high
10 –  CAN bus, low
11 –  Display voltage supply, positive, optional for radio module low version only
12 –  Voltage supply, negative, terminal 31
13 –  Display HV CAN bus low, optional for radio module low version only, not for midline
14 –  Display HV CAN bus high, optional for radio module low version only, not for midline
15 –  Voltage supply, positive, terminal 30
16 –  Anti-theft coding control signal, SAFE, positive

So this means we need to cut the cables that connect to pins 9 and 10. These cables are brown and purple on the Autoleads SOT-967 harness, remember you do not want to sever the connection between the male and female Quadlock connectors, you just want to tap into the cables with the appropriate cables from your Bluetooth harness, once done you will have a connection that looks like this:



I would suggest that whilst you have your soldering iron handy, this is also a good opportunity to modify your microphone cable so that it will route via the RNS-510 so you can use the mute function on the RNS-510 and use voice commands, this is easily done using a length of microphone cable and some VW repair wires, a guide ton how to do this can be found here:

http://www.my-gti.com/1234/volkswagen-rns-510-microphone-connection-for-voice-control

Anyway, now you just need to wrap the cables with some good quality harness tape and add a bullet connector to the remote output cable with a crimp tool and you have a finished PnP harness. Once finished you will end up with a harness that looks something like this:



If you were wondering why I suggested keeping hold of the female speaker ISO connector that you cut off earlier on, it is so you can connect it up to the end of the speaker cables coming from your amplifier, if you route this through to behind the stereo then you simply need to connect it to the male speaker ISO connector on your wiring harness meaning that you do not have to cut or modify any of the standard speaker cables in your car – Simple! When it comes to fitting it’ll look something like this (please excuse the iPhone camera photo):



Assuming you have already fitted your amplifier (Pretty straightforward so I won’t detail that here) you are now ready fit your new PnP harness, so simply disconnect the Quadlock connector behind your stereo and fit your new PnP harness between the stereo and the car’s Quadlock connector. You then need to connect everything else up behind your stereo (RCA output, speaker cables, amplifier remote power output, Bluetooth harness and microphone cables), refit the stereo and you’re done. Once connected, you will need to recode your stereo via VCDS/VAG-COM as the speaker out put needs to be changed from “output stage power 26 dB” to “output stage line-out 12 dB”, there is a good guide on how to do this here:

http://www.my-gti.com/1411/volkswagen-rns-510-coding-when-installing-with-a-factory-amplifier

Once recoded, you are ready to enjoy your standard VW headunit with any off-the-shelf car amplifier that you have fitted, for me this is the perfect solution as I have retained a completely standard looking interior but now have far superior sound reproduction thanks to the hidden amplifier. I would also recommend changing the standard speakers for higher quality units as well, but that is not something I’m going to include in this guide. Now, sit back and enjoy your new improved car stereo, I think you’ll agree it was worth all the hard work you’ve put into this!

[Rax]

Hi

This "how to" is just what I was looking for however I have a RCD-310 HU and was wondering if the exact same pnp harness would work?

Thank you.

[mortygttdi]

Rax It should be the same for more or less every VW headunit, just look on My-GTI.com to see if there is any wiring changes between the model years? I think the only change is the aux/cd ground cable and the bluetooth mute position changed.

Darren

[Rax]

Thanks Darren I'll have a look.

Another question, I have purchased a 2 channel LOC (Phonocar 5/142) but the speaker splicing wires on it are labelled as Front Left+, Front Left -, Front Right+ & Front Right-.

Does this mean I have to splice into the front speaker wires? I thought the rear speakers were the wires to splice for a signal? Does it matter wether the fronts or rears are used, Or can I just ignore the labels on the LOC and splice into the rears?