Fog lights, GTI vs. TDI, schematics

[User1138]

I have a '17 GTI S. I was driving through the snowy woods (as an official at a winter stage rally) and, courtesy of unusually low snow, I found something very solid under the snow at speed. It was nearly as wide as the car and an inch or two taller than underside of the car. It broke the core support and put enough vertical force into it to rip a mounting lug out of the intercooler. All of that is replaced and working fine now. And it was an excuse to upgrade the intercooler.

It also caused the front bumper to flex enough to break all of the rigid plastic structures inside the left side of the bumper, like the center grill, the mounting for the left fog light, and the left fog light grill. The paint is cracked in places. I have collected the parts to get it back together.

In the meantime, I had a spare TDI bumper lying around from someone who made a GTD out of a Golf TDI. I installed it on my GTI while I put the original bumper back together.

It has been a few weeks and I kinda like the look of the TDI bumper on my car. However, the TDI fog lights uses halogen bulbs and the wiring in my car is for GTI LED fog lights. As near as I can tell, there is no model of Golf sold anywhere in the world with a LED fog light that fits the TDI bumper. If you know otherwise, let me know.

Is there some point in the wiring harness to the fog lights where LED or halogen harnesses can be swapped in and an adaptation for the other type of bulb set? Are the wiring schematics that show the fog lights for the GTI and TDI available anywhere? I'd be willing to pay if I knew I was getting the info that I am looking for.

 

[Jachas]

The easiest way would be to use adapter harness from LED GTI to halogen TDI, but because halogen need more power, could be that halogen wiring have thicker cables (1.5mm2 instead of 2.5mm, for example) If you have thinner cables, I recommend to use LED bulbs in place of halogen

AFAIR LED connector should be 4F0973702 (if you can confirm, would be perfect). If so, for adapter you would need 5Q0973802 connector + pins and correct to halogen bulb connector (H8 or H11, I don't remember) + pins


Coding would be needed only if you use halogen bulb, if LED, there is a change that coding wouldn't be necessary

 

[User1138]

First, thank you for the good response that understands potential complications.

Are there good LED H11 bulbs? Every LED H4 bulb that I have tried fits in the reflector assembly and plugs into the connector but puts out the light in the wrong place. It comes out as a blob and, for example, doesn't have the sharp horizontal cut-off or extra light on the side away from oncoming cars that it has when a proper H4 halogen bulb is used.

The LED connector used in the GTI seems to TE MCON 1.2. "1.2" refers to the terminal pin width (in mm). The leads in the exposed harnesses are a gauge that one would expect for such small pins. Running halogen driving light wattage through them does not seem wise. So I hope there are suitable LED bulbs.

Thanks for the part number. I was looking for a connector from Mouser/Digikey/etc. but it looks like there might be some keying (i.e., only one orientation for connecting) on the connectors they sell and the connector latch is on the opposite side.

Given how VW like to design things with lots of commonality to increase volume/reduce cost per part, I would be surprised if that smaller gauge wire is used all of the way to the main harness but maybe it is.

 

[Cuzoe]

I'll post up schematics for both later this evening when the kiddo is asleep. You can just change them light type for those two adaptation channels in the BCM to match the type of bulb you install. I'll post those too.

The schematics will show the wire diameter. If VW used a different diameter wire it probably does go all the way to the BCM. If I remember correctly, there are no disconnects for the headlights/fogs between the BCM and the headlights. Remember that firewall feed through is only inches from the BCM anyway.

 

[Jachas]

Are there good LED H11 bulbs?

I don't know if is available in US, but in EU OSRAM and PHILIPS LED in some countries like Germany, Austria, Spain, Italy,etc. are homologated to use on roads, so the quality of light must be there in order to receive such homologation. Maybe not the cheapest, but at least with price, comes the quality

 

[Cuzoe]

Seems I don't have (or at least can't find in my files) the GTi drawing, will keep looking. Drawing from the Golf is below.

The *4 says depending on equipment, which I suspect is either halogen or LED fogs. If that suspicion is correct... I'm thinking LED lights get the 1.5mm (16 awg) wire straight through. And the halogens get the 2.5mm (14 awg) to the bulb, but near the BCM that wire is spliced to a short 1mm (18 awg) wire. The 2.5mm likely won't fit into the BCM plug so the wire is stepped down prior to the termination.

The coding is here, courtesy of @DV52. In your case you'll make the opposite changes since you're going LED to Halogen (the post is for someone going Halogen to LED).

 

[Jachas]

If I am wrong, anyone feel free to correct me, but 55W at 13,5V is around 11Amps. On the "AWG to AMP" tables on internet, 1.0mm2 cable is rated to around 12Amps, so if 1.0mm2 is capable of handling halogen, 1.5mm2 (which we suppose gonna be with LED fog lights) gonna be enough to handle both LED or halogen (only question is if the pins in the connector are capable of such power output)


If you want extra margin on safety, when coding you can change power output from 100% to 90% (and power the bulbs with around 49,5W instead of 55W) (less light, but extra safety on harness)

 

[DV52]

@Jachas hmmmm.........no offense - but I don't think so!!

When I was learning this stuff (many years ago) Watts = Volts x Amps .

The formula actually involves "real" and "imaginary" power elements that together form something called the "Power Triangle" - see below

However - for DC systems, the angle shown in the diagram effectively becomes zero and the complicated bits disappear. This means that we need only worry about Real Power (in Watts) for battery operated circuits

So transforming the equation: Amps = Watts divided by Volts = 55W/13.5V =~ 4 Amps

On my wiring diagrams the wire size(s) is as shown in @Cuzoe post. Note that a 1 mm2 wire is used from the BCM to C69 -which is a splicing point for the fog light in engine compartment wiring harness. From that point to the fog-light fitting, a 2.5 mm2 wire is used.

VW is NOT known for putting more copper in their cars than is absolutely necessary. My hunch (guess really) is that the increased cross-section wire is meant to reduce VD ( being "Volt Drop", not the sexual disease!!)

Don

 

[Jachas]

@Jachas hmmmm.........no offense - but I don't think so!!

When I was learning this stuff (many years ago) Watts = Volts x Amps .

The formula actually involves "real" and "imaginary" power elements that together form something called the "Power Triangle" - see below

However - for DC systems, the angle shown in the diagram effectively becomes zero and the complicated bits disappear. This means that we need only worry about Real Power (in Watts) for battery operated circuits

So transforming the equation: Amps = Watts divided by Volts = 55W/13.5V =~ 4 Amps

On my wiring diagrams the wire size(s) is as shown in @Cuzoe post. Note that a 1 mm2 wire is used from the BCM to C69 -which is a splicing point for the fog light in engine compartment wiring harness. From that point to the fog-light fitting, a 2.5 mm2 wire is used.

VW is NOT known for putting more copper in their cars than is absolutely necessary. My hunch (guess really) is that the increased cross-section wire is meant to reduce VD ( being "Volt Drop", not the sexual disease!!)

Don

Your right, for my defense, I just woke up when I was writing my post

But in this case (LED to halogen swap), is even better news. Plus I found that declared max current by TE-connectivity LED connector (1-1670916-1 and 1-1703498-1) is 25Amps

 

[Cuzoe]

Although I don't think there's going to be an issue with the wiring, I would not go by the max power than any connector/pin can handle. What is shown for a connector/pin is going to be based on the largest wire that can possibly fit in the pins that are spec'd for that connector. And a pin being a solid, albeit small, piece of metal is going to have higher power handling capacity than any stranded wire.

In aircraft wiring it's not too uncommon to see a long run of wire stepped down to a slightly "smaller" relative termination size at the pin because connector power handling is not typically what dictates the needed wiring. Obviously we're not talking stepping down 8 gauge to fit into a 22 gauge sized pin (with whatever amp rating that pin comes with).

That's a whole lot of typing to basically say you don't want to look at what a connector can handle. It's almost always going to be much more than the wiring that you're bringing to that connector .

 

[User1138]

I have owned a number of 70s and 80s British cars that didn't use relays for the high beams and powered those lights through the high-/low-beam switch. With uprated bulbs, it was common for the switch to melt into the high-beam position. So I get paranoid about running too much power through car electrics.

I intend to use LED bulbs. I have found them from Phillips and Sylvania on this side of the Atlantic.

The Sylvania one is "plug-and-play" with a box to keep the car's computers happy integrated into the wiring. The datasheet that I found (but not from Sylvania) says 12W.

The Phillips one can be purchased with or without the box. Phillips says their supllier for North America is Lumileds. Their datasheet says 20W.

Do I need the box? If I go without the box, any idea what I need to do as far as adaptation?

 

[Cuzoe]

Box allows you to leave the halogen coding as is. If you go to an LED without the box it's possible you will get a fault for the lights. But you can resolve that by changing the light type in the BCM adaptations.

Clearly I didn't read to the end of your post, haha. Just change the light type to LED. Being these won't be factory LEDs, you might have to try a few different LED types before you find one that is fault free, or the first choice may work. There are several options in the adaptations but I'm sure one of them will do it.

 

[DV52]

In aircraft wiring it's not too uncommon to see a long run of wire stepped down to a slightly "smaller" relative termination size at the pin because connector power handling is not typically what dictates the needed wiring.

@Cuzoe: Of course I bow to your superior knowledge about the aircraft industry and I totally understand your point- BUT, there is an entirely different dynamic at play when deciding wire-sizes on a modern car!!

The difference is because the economics that underpins mass produced vehicles is very different to the production-line for aircraft.

The sheer number of cars that roll-off the convener-belt focuses the mind of decision makers on copper efficiency - in particular optimizing the size of the each strand in every wire with the electrical load and matching the result to the size of the terminating pin.

In days now past - copper was cheap and it was more cost-efficient to not create different wiring looms for the same model vehicle. This meant that there was often more copper in these cars than needed. But those days are long gone!! With modern mass market production equipment and with the increased cost of copper - it's now more profitable to build different size wiring looms with just the needed amount of copper!!

Hence VW's abhorance for excess copper in their cars!!

Don

 

[DV52]

.................any idea what I need to do as far as adaptation?

The coding is here, courtesy of @DV52. In your case you'll make the opposite changes since you're going LED to Halogen (the post is for someone going Halogen to LED).

 

[Cuzoe]

In private aviation the driver for wire size, outside of the electrical necessity, is going to be weight (and to a lesser extent the size of harnesses). There's not going to be any unnecessary wire, although cost of wire isn't much a concern when you're talking about 20+ million dollar airplanes with production numbers typically in the low-mid hundreds.

And I should be more specific that often when we see wire stepped down it's because these are long runs where voltage drop becomes a concern. We're not facing that issue in our cars. Basing anything on how much power a connector can handle is, in my experienced but very much subjective opinion, not a great idea.

For what it's worth, I'm personally averse to excess wire size because I spend a lot of my time building harnesses and having to route those harnesses in places where they were not intended . In contrast, I am very much in favor of adding provisional wiring so that I don't have to access or route in a given area again.