Retrifit fog lights - connecting the light switch

[sunnyorca]

Hello, I'm a newcomer to the forum, and having gone through numerous posts, it's evident that this community is exceptionally friendly and open! Kudos to everyone for maintaining such a positive atmosphere!

I'm going to retrofit the front fog lights on my Golf, which already has a rear fog light.

I've found some nice installation & programming instructions (1, 2, 3).

It's clear how to connect the fog lights to the BCM (pin 5 & 45 of the connector B).
However I'm not sure about the light switch. On the stock light switch (EU version), all pins are occupied except for the pin 7. On the connector there is no wire going to that pin, while on the new light switch the pin 7 is occupied (see the picture).

It's often mentioned (1, 2, 3) that the pin 7 is not used and it's enough to have only a pin 5 for both rear/front fog lights to work, but why is it then occupied on a new switch?

Pretty much all of the aftermarket switches with a front fog light function have the pin 7 occupied and it makes me suspect that it is actually used.

 

[Jachas]

I would try to run in without messing with switch wiring. Just code fog lights and try to run changing only the switch. If it doesn't run, then check the schematics where it goes and do the wiring

 

[DV52]

However I'm not sure about the light switch. On the stock light switch (EU version), all pins are occupied except for the pin 7. On the connector there is no wire going to that pin, while on the new light switch the pin 7 is occupied (see the picture).

It's often mentioned (1, 2, 3) that the pin 7 is not used and it's enough to have only a pin 5 for both rear/front fog lights to work, but why is it then occupied on a new switch?

Pretty much all of the aftermarket switches with a front fog light function have the pin 7 occupied and it makes me suspect that it is actually used.

@sunnyorca: Hmmm.................. this is the "official" wiring diagram for the factory rotary Light switch on a Golf mk7/mk7.5:

"J519" in my picture =Body Control Module (BCM) in VCDS, or Central electrics module in OBD11 speak.

For those reading this post who are NOT familiar with the nomenclature that VW uses on their wiring diagrams - notice the Earth connection has the label "T10 /6 31". This means:

• T10 = Connector with a total of 10 x pin positions
• /6 = pin #6
• 31 = Terminal 31 - this is another way to define earth as per DIN standard 72552

Notice that the factory wiring loom for a rotary light switch with fog-light capability has a wire-count = 9! Also, note the absence of T10 /7 on the light-switch which means that pin #7 is definately NOT USED on the factory light-switch

So, my hunch is that on the non-OEM light-switches that you show in your pictures - pin #7 is used to provide a contact for the non-OEM light sensor (see below) that piggy-backs into 10 x pin connector.

Don

 

[DV52]

I would try to run in without messing with switch wiring. Just code fog lights and try to run changing only the switch. If it doesn't run, then check the schematics where it goes and do the wiring

@Jachas: Hi.

If OP does NOT want to change the rotary light switch - he/she can code the front-fog lights to operate when the rear fog lights are activated (i.e. front and rear fog-lights operate together). Or he/she can code the front-fogs to work with any other lighting function on the rotary light switch
Don

 

[ZERO815]

If OP does NOT want to change the rotary light switch - he/she can code the front-fog lights to operate when the rear fog lights are activated (i.e. front and rear fog-lights operate together). Or he/she can code the front-fogs to work with any other lighting function on the rotary light switch

Hey Don,
Unfortunately this is not legal in Germany, and you won't pass TÜV inspection. Every light that is installed needs to operate "after" the books. About 25 years ago my MK2 failed inspection because I was running used big bumpers. They came with front fogs, but I haven't had time to wire them up yet. After removing the front fogs in the parking lot my car passed inspection.

 

[DV52]

@ZERO815: OK, good to know - I've always wanted to live in Germany, but Ich kann kein Deutsch (alas)! Here in the land down-under, we don't have TÜV inspections - not sure if this is better, or worse than Germany.

I guess if anyone wanted to take-up my suggestion, they should include a connector in a handy position that could be easily unplugged before the vehicle inspection!!

Don

 

[carbon_gecko]

So when I added front fog lights to my mk7 base golf s I had to run the wires from the fog lights to the BCM and a wire from the BCM to the new radial knob, then in VCDS did long coding for front fog lights, then adaptions for when to activate. If all your rotary pins are used, run the front fog wiring, you probably have the signal wire already and just need the coding. Additionally when i used the aliexpress auto sensor i never had anything in pin 7, when i retrofitted the rain/auto sensor it filled some pins but 7 remained empty.

 

[sunnyorca]

Hey, @DV52, thanks for clarifying the wiring. I'm definitely up for installing a new switch. And I hope it will pass TÜV
I'll give it a shot this week with a stock connector and see how it goes!

@carbon_gecko I'm glad you could make it!
Which new wires did you run from the new switch by the way? I assume it's pin 5 to BCM A/29.

include a connector in a handy position that could be easily unplugged before the vehicle inspection!!

I believe to pass TÜV, it's not permissible to have any equipment installed on a vehicle that isn't operational (e.g., you can't turn it on). So the only solution is to physically remove the fog lights, as @ZERO815 has described.

non-OEM light-switches that you show in your pictures - pin #7 is used to provide a contact for the non-OEM light sensor

It's interesting that the only switches with 9 pins that I could find for sale were used ones from other vehicles, and all the ones with 10 pins were non-OEMs.

 

[DV52]

It's interesting that the only switches with 9 pins that I could find for sale were used ones from other vehicles, and all the ones with 10 pins were non-OEMs.

Yes, it is "interesting".!!

As I have said - the reason for the 10th pin on non-OEM rotary light switches is because of the introduction of non-OEM light sensors that piggy-back onto the connector.

But it shouldn't matter - the non-OEM switch should work OK if you use it on a car that has either NO light sensor, or it has an OEM light sensor (because the 10th pin isn't used).

Don

 

[carbon_gecko]

Hey, @DV52, thanks for clarifying the wiring. I'm definitely up for installing a new switch. And I hope it will pass TÜV
I'll give it a shot this week with a stock connector and see how it goes!

@carbon_gecko I'm glad you could make it!
Which new wires did you run from the new switch by the way? I assume it's pin 5 to BCM A/29.


I believe to pass TÜV, it's not permissible to have any equipment installed on a vehicle that isn't operational (e.g., you can't turn it on). So the only solution is to physically remove the fog lights, as @ZERO815 has described.


It's interesting that the only switches with 9 pins that I could find for sale were used ones from other vehicles, and all the ones with 10 pins were non-OEMs.

Yes, pin 5 five to a/29, additionally, I forgot to mention I had to upgrade my BCM to one the had foglight pins 087T>>087AA

 

[sunnyorca]

Finally activated the fog lights, works like a charm with the new switch!