Your lighting circuit is not designed to handle the extra load a light bar would place on it.

Typical installation would be to use a relay that is switched with your high beams and direct battery power routed through the relay's normally open contacts to power the light bar.

The power necessary to energize the relay coil shouldn't trigger an error & you don't need a canbus module.
A relay coil will only draw ~0.15A when energized, but will allow you to switch as much current as needed (depending on the size of the relay contacts)

Recommend a HELLA 003530041 relay or similar to do the switching (HELLA is fused & can handle up to 25 amps). Wire power from your battery to your lights using appropriate wire gauge as recommended by your light bar manufacturer.

 

Your lighting circuit is not designed to handle the extra load a light bar would place on it.

I did something similar - running for a year every day, the circuit is oversized quite, able to handle extra load - besides the LED does not load too much.

 

the circuit is oversized

I really don't think Audi would waste money (and weight) putting in wires that are thicker than necessary. The circuit will be designed to cope with the most adverse set of loads and environmental conditions that could be experienced anywhere in the world (high air temperature is likely to be the driver).

Tapping into power circuits is bad practice (what else has been added before? And you've reduced the reliability of the lighting circuit by introducing additional failure modes). Do the next owner a favour and do it properly without butchering the standard wiring. Also there are quite a few C and U regs concerning lighting, is what you are doing legal where you live?

 

the circuit is oversized

I really don't think Audi would waste money (and weight) putting in wires that are thicker than necessary.

Audi has few types of standard thickness wires - therefore they need to choose one of them (they dont use hundred types of wire for every load) , which have overheads beyond.
They control the Amper via fuses, not only with the thickness.
As I said, I did the same, it had not any affect so far, and I dont expect problems ever.

 

Your lighting circuit is not designed to handle the extra load a light bar would place on it.

I did something similar - running for a year every day, the circuit is oversized quite, able to handle extra load - besides the LED does not load too much.

The OP didn't state which light bar is to be used. Without that information you have no idea what the current draw will be. Without knowing the current draw you can't possibly know that the factory wiring is sufficiently sized.

Maybe you got away with it on your car, but advising someone that everything will be OK is dangerous.

 

As both FNChaos and John949 have commented, there are a number of reasons why it is not advisable to randomly tap into an existing wiring harness for non-standard project and think it's all going to work out okay.

One of the first points that many people don't fully understand about Audi's electronics is the use of PWM for providing power to the various circuits. Suffice to say, if you don't know what PWM is, or how it works, you have no business cutting into a wiring harness in the first place.

There's also the issue that many of the wiring harnesses in the TT are interconnected to other circuits and/or controllers and are all "set" by the factory codes. Adding puddle lights or an auto dimming mirror requires more than just splicing into the wiring harness. Code changes are often necessary so the car "knows" what's going on and can function correctly with the new circuitry.

Without fully understanding exactly what you're cutting into or where those wires lead to or even what they're interconnected to could cause functional, performance or even safety issues; (e.g. pyrotechnics in airbags and seat belts). And if you can't read or understand a wiring diagram, please do yourself and the next potential owner a huge favor and leave electrical modifications to people who know what they're doing.

And finally, while the Forum encourage members to share their knowledge and experiences, please don't make technical recommendations unless you know exactly what you're talking about.

.

 

Without fully understanding exactly what you're cutting into or where those wires lead to or even what they're interconnected to could cause functional, performance or even safety issues; (e.g. pyrotechnics in airbags and seat belts). And if you can't read or understand a wiring diagram, please do yourself and the next potential owner a huge favor and leave electrical modifications to people who know what they're doing.
.

I know what a PWM is and have no problems reading a wiring diagram. This post was more to try to see if anyone had learned anything when they tried to do it.

I am planning on tapping into the signal wire for the high beams, connect them to a relay and connect that to a Strands Siberia SR12 LED bar, which I will mount behind the grill, just below the licence plate. I am going to use a voltmeter to see if my TT has a continuous 12 v stream to the high beams. As far as I am aware, if there is, there shouldn't be any issues.

 

@ Wehler - The point wasn't aimed at you, just a general comment. ;-)

Auxiliary lights are not a common modification for the TT, however I did find this posted on another Audi Forum for a Q7 - 160W LED light bar under the front license plate, and two 6.5" 36W LED Bars behind the grille. I would guess the circuitry would be pretty similar.

FYI - we have a whole set of Workshop Manuals if you need any wiring diagrams or information on pulling the bumper, front grill, etc. Also check the Knowledge Base as there's a ton of various projects in there which may help.

FAQ - Audi TT (8J) Workshop Manuals & Self Study Programs
https://www.ttforum.co.uk/forum/viewtop ... &t=1833829

Auxiliary Driving Lights Installed
https://www.audiworld.com/forums/q7-dis ... d-2917692/

This UK website Lazerlamps offers CANM8 signal management systems to interface with a relay and high-beam circuit. The TT (8J) 2007 is listed on the compatibility list so it may be worth contacting them for more information -

HOW TO: CANM8 High Beam Interface

Lazerlamps: Lazerlamps Home Page
CANM8 CANNECT PARK ONE (R)

This link will open Lazerlamps VW Golf installation guide. Obviously not exactly like the TT, but it should give you a pretty good idea of what's involved in fitting a light bar into a TT.

https://www.lazerlamps.com/mpattachment ... ct_id/451/

If you want to build your own wiring harness and just want the CANM8 interface, you can check out their website here -

Last but not least, a link to Hella Auxiliary lights. They may have some additional information or products specific for VAG vehicles. The wiring diagram below is for their LED lightbar with a simple on-off switch without a CAN module.

https://www.hella.com/techworld/uk/Car- ... hts-46329/

 

@ Wehler -
FYI - we have a whole set of Workshop Manuals if you need any wiring diagrams or information on pulling the bumper, front grill, etc. Also check the Knowledge Base as there's a ton of various projects in there which may help.

Do u know of any videos explaining how to remove the grill without damaging the grill or having to remove the entire front bumper?
I also have the European version of the TT. By the looks of the manual u linked, it seems to be different to the American version. Less screws

 

As far as I understand, the grill can't be removed without removing the entire bumper.

You might want to try the Knowledge Base and Forum search function. A quick search found these old posts and for reference, it's covered in the Workshop Manual listed below -

FAQ - Audi TT (8J) Workshop Manuals & Self Study Programs
General Body Repairs, Exterior (Convertible Top) - RG 50 55 57 61 63 64 66 - A005TT00220
https://www.ttforum.co.uk/forum/viewtop ... &t=1833829

How To: - Install a New Bumper Grill
https://www.ttforum.co.uk/forum/viewtop ... 3&t=332537

Mk2 TT honeycomb grill?
https://www.ttforum.co.uk/forum/viewtop ... 9&t=997049

TTRS bumper removal and grill install
http://lz7w.blogspot.com/2014/04/ttrs-b ... stall.html

 

Your lighting circuit is not designed to handle the extra load a light bar would place on it.

I did something similar - running for a year every day, the circuit is oversized quite, able to handle extra load - besides the LED does not load too much.

The OP didn't state which light bar is to be used. Without that information you have no idea what the current draw will be. Without knowing the current draw you can't possibly know that the factory wiring is sufficiently sized.

Maybe you got away with it on your car, but advising someone that everything will be OK is dangerous.

Just adding for completeness and for future reference: the wiring is also only part of the circuit - the power for the lights runs through control modules, so even if the wiring is capable, it is unknown what the internal circuitry in the module could handle. Something else to consider when adding an extra circuit without using a relay method

 

+1 MT-V6 - Exactly! This is why both of the above wiring diagrams shows power for the auxiliary lights coming directly off the battery with an appropriately rated in-line fuse.

 

+1 MT-V6 - Exactly! This is why both of the above wiring diagrams show power for the auxiliary lights comes directly off the battery with an appropriately rated in-line fuse.

One of the reasons I like & recommend the HELLA relay, it comes with a built in fuse holder. [smiley=thumbsup.gif]

http://hellahd.com/index.php/default/electrics/relays/mini-iso-relays/12v-spst/003530041/

 

+1 FNChaos - Oh, nice find!! I wish I'd known about that when I did my Reverse Camera installation.

Regarding the fitment of Auxiliary lights in Europe and the UK, you may find this worth a read -

Buyer's Guide - ECE Regulations and Keeping it Legal
https://www.lazerlamps.com/news-media/p ... g-it-legal

Looking through the Laserlamps VW Golf installation instructions (PDF download below) CANM8 also also offer a Contactless CAN Reader so you don't have to splice into your vehicles CAN wires -

"The Contactless Reader allows for reading the CAN-Hi and CAN-Lo vehicle data without any actual metal to metal connection between the interface and the vehicle CAN wiring."

Wouldn't be a bad idea if you wanted to remove the auxiliary lighting system at some point and put it all in another vehicle.

The Laserlamps wiring harnesses includes the 12V relay, an inline fuse and there's also an on-off switch so the auxiliary lights don't always come on when you turn on the high beams. You'd just need to add the CANM8 Interface and maybe the Contactless CAN reader and you're good to go.

View attachment VW Golf Installation Instructions.pdf

 

I wrote to Aaron Green at Lazerlamps and he was kind enough to reply with the following information and photo. I would encourage anyone who's interested in their products or installation of an auxiliary light system for the Mk2 to checkout their website and contact Lazerlamps directly -

Thank you for your e-mail and interest in our products.

We have an employee here who has a Mk2 Audi TT to which I have already completed a simple installation using the numberplate mounts (photo attached). At the time he didn't want the grill on the vehicle cut but after seeing an installation I carried out on an Audi A6 Avant last week. He has now asked if I can cut the grill to sink it into the lower grill when the better weather is here and we are less busy which I believe will be a simple installation providing people are happy to cut their grill.

Just to clarify for you, this car is a 2008 and has the xenon OEM lamps. I was able to find a 12v high beam signal at the headlight assembly. The lamp has been on the vehicle now for over 2 years without any issues from the PWM/can system. As a relay only draws 0.15-0.25ma to energise I believe that this is well in the tolerances that are allowed in the Audi software for this vehicle hence why it has been fine and 'to the cars knowledge' it doesn't know the relay has been added and everything is fine.

How To Locate 12V High Beam Signal Wire
https://www.youtube.com/watch?v=CrCY7cH ... e=youtu.be

In fact we have had zero issues with splicing into the high beam circuit on any vehicle that displays a 12v high beam signal including new vehicles with Led headlights; (e.g. VW T6.1, 2020 Defender, VW Amarok, MAN TGE) to name a few. With the A6 Avant and the R8 I installed to there was no high beam signal at the headlight (in fact about 4 wires, 2 of which are twisted hence Can) so we needed to use a Lazer Can Interface to generate the High beam signal.

Of course if you feel more comfortable to use the Can interface then this will work regardless if the has a 12v High beam signal or not, but from my experience if the signal is there, I will use it as it not only saves time on the installation (Can interface can take up to an hour to fit) and also the interface is £114.

Unfortunately I don't think we would be looking to develop a vehicle specific kit for this vehicle, however If you believe there would be enough interest in the solution I can put forward the idea of making the instructions but I would be very doubtful it would be something that is published on the website. I can store any installation instructions and email them when and if needed.

Best Regards - Aaron Green, Lazerlamp