Halogen to LED's

[Hez5]

Hi

I'm so confused. I have a 2015 Comfortline with halogen tail lights.

If want to upgrade to LED's (without progressives) - what do I need to do (apart from buy the LEDs). Do I need to just buy and adapter and it should work? Do I have to rewire?

Thanks in advnace.

[DV52]

Hez: so perhaps I'm oversimplifying my understanding of your question. If all that you want to do is swap halogen for LED bulb-by-bulb - why do you need an "adapter"? Why wouldn't you just buy LED lamps that are mounted on the appropriate base?

But - if you want to swap halogen for LED - by changing the entire tail light fittings, then the fundamental problem that you need to solve is how to electrically drive the additional lamps on the LED assemblies (there are physically more lamps on LED tail fittings).

You can take the "purist" approach and run additional wires back to the BCM (the module that controls all of the exterior lights on a mk7). Or, you can trick the BCM by thieving the existing wires on the halogen tail light plugs. This involves using what's called a cross wiring harness and basically it connects together on both sides of the car lamps that have the same function (like the brake lights and the parking lights and the reversing lights). This leaves unused wires that can be connected to the additional LED lamps (coding changes are needed for this method to work properly).

Don

[Hez5]

Ok ... thanks for that detailed response.

Where do I buy this harness? I think I know who can do the coding. But its not clear which harness as most harness is for the progressive tail lights?

HL

[Sharkie]

Have a look at these guys, lots of options VW Golf Mk7 LED Tail Lights - Supernova Lighting

May need to wait for them to get stock in though.

[ideefixxe]

Hello Everyone,

Has anyone retrofitted the Golf R (circa 2014 / 2015) smoked LED tail lights with that of a Golf 2014 / 2015 tail lights?

I noticed there are no harnesses readily available for retrofitting the tail lights.

With the kind of dil I am, I procured OEM Golf R tail lights without doing any research. Now I am struggling to find some one in Melbourne who can assist me with the retrofitting.

Please, can someone share any information they may have.

[The_Hawk]

The bulb out warnings in modern cars work by measuring load across the circuit. The halogen bulb sucks current when it's working (and none when it's not). The problem with LEDs is that they draw so little power it sets of the warning.

Usually you have two options. Either "error free" LED bulbs or adaptors which essentially just waste power to put a load on the circuit, or code out the errors (which means you won't get an error if the bulbs ever die... although the adaptors essentially fake a working bulb anyway so you should check on them occassionally).

[DV52]

^^ ^^ if I could add to the responses thus far (above)- the Golf mk 7 has a couple of added features that helps in managing the differences between incandescent and LED lamps (as the Hawk has explained). It's a new set of smarts that was added to the Body Control Module (BCM - @ address hex09) when Golfs transitioned to MQB platform build.

On mk7's, power is supplied to the 35 x exterior lights using Pulse Width Modulation (PWM) which is just a fancy name for chopping up the DC power from the battery into short ON/OFF periods. The chopping (read "switching") process for PWM is used to set the illumination level of each lamp on the car: the greater to switch-on time compared to the switch-off time , the higher the illumination level.

The design of the BCM specifically caters for the each of the two lamp types differently and it's possible (and generally, it's recommended) that the settings in the BCM reflect the type of lamp that's installed in the car (this obviates the need to use "loading resistors" on retrofitted LEDs to stop CAN bus errors that the Hawk identifies in his/her? post). Although I haven't found any official VW literature to confirm my suspicion - I suspect that the BCM uses digital control for LEDs and it uses analogue controls for incandescent lamps.

The BCM also has a large library of PWM characteristics to suit the particular lighting function that each lamp performs - these can be selected separately depending on lamp type and the lamp function.

Here's a trace that I took using an oscilloscope to "view" the PWM with the BCM programmed to supply power to a LED lamp at an illumination level of 50%:



Notice the "chopped" DC trace and notice that the waveform period is 5 milliseconds (i.e. PWM frequency = 200 hz). Aslo notice that the "duty-cycle" of the waveform (the relative switch-on/switch-off time) is 60% notwithstanding that I programmed the BCM for 50% illumination.

If I reprogram the BCM for an incandescent lamp @ 50% illumination, the PWM frequency is halved and the duty cycle is 50%.

So- moral of this story is that although sometimes ignored when retrofitting LED lamps. it is worth telling the BCM on a mk7 to no longer supply power to the new lights as if they remained incandescent. The BCM has LED settings - and it's prudent to use them IMO

Don

[ideefixxe]

Just received a response from Car Systems. They have advised we wouldn't need anything apart from this -

Additional Wiring - LED Taillights VW Golf Mk 7