When driving on "AUTO" the adaptive light system is on, but the fog lights cannot be switched on.

When switching to perma low beam the fog lights can be switched on.

 

Is it possible to mod the switch so that in AUTO the fogs can be set to on without loosing adaptive lights?

I suspect all of that functionality is handled within the BCM & AFS controller software rather than by the wiring to/from the switch. If this is the case, I'm not sure that you'd be able to get the fogs to come on with AFS.

 

If you have VCDS it would be worth poking around in the coding of those controllers to see if there's anything there.

 

Tbh though, I'm not sure it's worth the effort: most of the AFS functionality is aimed at increasing headlight range in good visibility conditions. In fog it's mostly useless.

It feels like a hardware blockade to me.

The switch has a lot of cables on its back. How does it work?

Could it be that by moving the knob to foglight one cable is pulled from 0V to 12V and by that the fogs switch on?

 

Could this be reproduced by shorting two wires whilst having the lights in Auto and therefore signalling to switch on fogs while being blocked by the switch?

 

Just asking, as I have no clue how the contacts actually trigger something.

 

Could it be a hardware blockade and a BCM thing?

 

 

You mean to poke around in the long coding of these controllers? I already poked around STG9 a lot but AFS has no unit, only found headlight regulation which I believe it is not.

Edited 16 August, 20196 yr by mbgar

I doubt tweaking the light switch will help, you'll probably get an 'implausible signal' error flagged and the low/dipped beams will come on as a fail safe.

 

It's more likely you need to tweak the AFS master (address 55). For example, my MK2 Octavia has AFS in both 'auto' and 'on' positions

 

Got a full autoscan from VCDS you can post?

 

I just had a look at the wiring diagrams and the wires from the light switch run straight to the BCM which means the BCM is handling all of the functionality from there down. Physically there are two separate mechanical switches inside the headlamp switch: one for the parking/head/tail lights and a separate one for the fog lights. Each switch is set up to send 12 V to the appropriate pin on the BCM when activated.

 

Based on this, the likely operation is this: In the BCM, when a pin goes live, the BCM will detect that as an input and activate the appropriate output so when the switch is moved to 'Auto' for example, the BCM will poll other systems (rain/light sensor, vehicle speed) and if all checks out for headlamp activation it will send a message over CANBUS to the AFS master to switch on the headlights in AFS mode. If the switch is moved to the dipped beam position it will send a message over CANBUS to the AFS master to switch on the headlights without AFS active.

Based on this, you would need to be able to reconfigure the BCM to support AFS activation when the light switch is in the dipped beam position, either by reflashing the software or changing the coding, OR reconfigure the AFS master to activate AFS when it gets a dipped beam on command. @langers2k's comment above suggests the latter may be possible.

The headlight switch itself would need to be modified too.

 

The 'pull' position for the front and rear foglights is physically restricted when the rotary switch is move into the 'Auto' headlight position.

 

Edited 16 August, 20196 yr by silver1011

25 minutes ago, silver1011 said:

The headlight switch itself would need to be modified too.

 

The 'pull' position for the front and rear foglights is physically restricted when the rotary switch is move into the 'Auto' headlight position.

 

The coding mod would be to get the AFS master to enable AFS when the light switch is in the dipped beam position (where it would be to enable fogs). No modification of the switch needed.

I get that, but I was answering the OP, who specifically wanted front fogs and AFS with the switch in Auto.

2 minutes ago, silver1011 said:

I get that, but I was answering the OP, who specifically wanted front fogs and AFS with the switch in Auto.

 

I expect if they did modify the switch to allow that combination, they'd get an implausible signal fault code

 

 

Assuming I get time, I'll dig out my spare BCM at some point and see what happens