Okay so following the diagram below, it looks like the RED / blk coming out of the switch is what is getting triggered to allow the lights to turn on. If I cut RED / blk and run it to a +12V source (maybe ignition or I'll just find another wire that is hot with only ignition) my fogs should turn on with just the switch right?
06-07 Sedan Foglight Wiring Diagram (OEM)
Picture didn't work.
https://cache.gyazo.com/27b1e0f2f9c8a66b298c34e2d0ba353d.png
Not if the Relay Module's Front Fog Light Control Circuit inhibits the fogs when other beams are on (which I suspect is why it is there).
Is the switch with indicator #1 the Fog Light Switch?
Hence Indicator #1 is only on when the fogs are on?
Yes, that is the fog switch. I was told that the blue wire coming from the fog switch should be grounded. The Control Circuit inhibits the fogs when Highbeams are on (it'll turn them off)
Yes - blue to GND so the hi-beam (or whatever - it depends on local Regulations) does not cut out the fogs (if you want to disable that function - at your peril).
The RED / Black +12V source determines when you can switch your fogs on so moving that elsewhere makes the fogs independent of the head-light switching.
I'd be inclined to leave the Blue as is - why not keep the "off when illegal" or off when high function?
Only if it also inhibits fogs at other times might you consider rewiring that.
It also inhibits fogs from turning on unless the headlights are on. Thus operation is only on when lowbeams are on. I would like to be able to use them with the parking lights as well.
From what I see, it says with parking or headlamps. Hot In Combination Light Switch then picture of parking, the word OR, then pic of headlamp.
I am trying to understand why putting the blue from the switch to ground lets the switch function at all times. Why does it work? Isn't the blue still getting current through it?
I guess I need to know how the Fog Light Control actually works to understand it.
cyanide wrote:
I guess I need to know how the Fog Light Control actually works to understand it.
Yep - that's it.
In fact "WE" need to know to be sure...
But if I may tackle it this way:
If the blue was GND, then the fogs would be on whenever (1) the fog switch is ON, and (2) the red-black from the light-switch is hot.
But the blue isn't to GND. Why not? Maybe there is a condition where they want it OFF despite light-switch & fog switch being on (hot).
IE - when the hi-beam is on.
Does that make sense?
IOW, the Fog Light Control breaks the GND when we want the fogs to be off - or ensure they are off despite other things wanting it on.
There are various reasons it may be done that way.
Maybe they want "standard wiring and switches" as much as possible and they only need the GND "cut-out" in some countries. Hence they move blue from GND to the Fog Light Control module.
And that Fog Light Control module may vary from place to place - eg, off with hi in Europe; off with hi or low in Australia, etc (they are examples only - I'm not quoting actual requirements).
Sometimes it's a "master" or override control. EG - many things could combine on the hot-side to enable the fogs. But if something shorts etc, then breaking GND guarantees an OFF no matter what. (Except for fused relay contacts etc...)
What you do depends on what you want - ie, fogs anytime, or only on ACC or IGN, or with lights (parkers or beam) etc.
Other than using a 2nd relay in parallel with the fog relay with its own switch and indicator, the existing wiring will need "interception". IE - a diode inserted into the RED / Black so another diode-isolated switch can be added.
I'd prefer to insert adapters rather than cut existing wiring, though in big multi-terminal connectors I have been known to merely remove the required terminal and diode & split that. Hence relatively easy to return to standard configuration and transfer to the next vehicle.
Wow, that was an excellent explanation. Thank you for that.