Fog Lights as Daytime Running Lights

In Austria, it is legal to use fog lights during the day (with or without low beam headlights), provided they are original equipment and not aftermarket additions. Therefore, they can be legally used as daytime running lights.

Since my Citroen Jumpy automatically turns on the low beam much too late (while everyone else has been driving with their lights on for 20 minutes in the evening twilight, my Jumpy thinks it's still bright enough without ), I would like to reprogram the daytime running lights (DRL) as follows:


Lichtschalter      Abblendlicht      Nebelscheinwerfer
0       aus             aus       aus
1a    Automatik (aus)   aus         an
1b   Automatik (Abblend) an         aus
1c   Automatik (Fern)     aus         an
2    Standlicht         aus         an
3a    Abblendlicht       an         aus
3b     Fernlicht         aus         an
---
4    Nebel+Abblend/Fernlicht         an/aus         an
5    Nebel+Abblend/Fern+Schlussleuchte an/aus         an



Line 1c and 3b because you have better visibility in the near range with high beams. It's true that it's a waste of energy, but you only use high beams for a tiny fraction of your total mileage, so it's negligible.
Of course, this only works when the engine is running, i.e., when the ignition is on.

'That means I need a circuit that turns on the fog lights when either the low beam headlights are off (1a, 1c, 2, 3b), or the fog lights are explicitly switched on (lines 4, 5) – but not when the rotary switch is explicitly set to 'off' (line 0).'

Using two classic relays in parallel, it would be difficult to achieve the desired result solely with input from the headlight wiring.
a) Relay A activates when fog is detected (lines 4+5).
b) Relay B activates when the low beam headlights are off (lines 0, 1a, 1c, 2, 3b).
Unfortunately, relay B also activates line 0, meaning that even when the rotary switch is explicitly turned off, it still turns on.

Can the position of the light switch on the turn signal lever be determined via the CAN bus, and can this be used to explicitly distinguish 'off' (line 0) from the other states? Specifically, can it be distinguished from the 'automatic (off)' state, which is line 1a?

Or is there already a ready-made CAN-BUS module available for purchase that implements the desired functionality?

Ideally, it would be great if you could simply switch the on-board computer into an 'Austria daytime running light' mode, where this specific table would be implemented...

Quote:

Am allerbesten wäre es natürlich, wenn man einfach den Bordcomputer in einen Österreich-Tagfahrlicht-Modus schalten könnte, wo genau diese Tabelle realisiert wäre...

Genau das dachte ich mir beim Lesen der Tabelle auch. Dummerweise geht das bei Modellen aus dem VAG-Konzern relativ einfach, beim Citroen habe ich keine Ahnung.
Gibt es denn kein Modell, aus dem Du das passende Steuergerät in Dein Auto setzen könntest?

Viele Grüße, Rainer

Ideally, it would be best if one could simply switch the on-board computer to an Austrian daytime running light mode, where this exact table would be implemented...

That's exactly what I thought when I read the table. Unfortunately, it's relatively easy to do with models from the VAG group, but I have no idea how to do it with a Citroen.
Is there no model from which you could extract a suitable control unit to install in your car?

Control unit = onboard computer? Or what exactly do you mean by 'compatible control unit'?

'Sorry, I'm a CAN-BUS beginner. I asked a similar question in a brand-specific forum, and the response I received was that the light switch is connected to the CAN-BUS, so you can't directly read the 'explicitly off' state (line 0) analogically to solve the problem with 2-3 relays.'

How can I find out if it's possible to reprogram the BC (presumably referring to a specific device or system)?

Quote:

Steuergerät = Bordcomputer? Oder was genau meinst Du mit 'passendem Steuergerät'?

Bei VAG kümmert sich das Bordnetzsteuergerät in Verbindung mit dem passendem Lichtschalter um Dinge wie Tagfahrlicht. Gibt es denn bei Citroen kein Modell, wo das Feature "Tagfahrlicht" bereits gelöst ist und man Teile übernehmen kann?

Viele Grüße, Rainer