Fog Light Anytime Mod??

I am taking a guess here, but maybe a wire from the OBD port could meet this condition?

 

What wire do we need to remove to have the fogs on when the brights are on?

 

You would cut the green wire. Or better yet, remove the entire C3 relay since its only function is to limit when the lights get power. The black wire just needs to be grounded when power is on.

 

Is that relay in the fuse box? Or is it inline with the wires? I've never been good with wiring diagrams.

 

Unfortunately the relays are integrated into the interior fuse box.

This thread contains a good deal of information on fogs: c foglights | Page 7 | PriusChat

This guy specifically was able to remove the fuse box and solder the relays on a Prius C: Custom Prius C Foglights (pictures, and instructions)

Sadly the relay wiring is more complicated than I expected and actually connects to the ECU which makes this even more complicated. I will continue researching and post any updates I come up with.

 

More wiring diagrams retrieved from the other thread:

 

BTW, there is never any situation where you would want fogs and high beams on together, that is why they limit the electrical load by preventing that.

 

Yeah... you'd never want visibility down low on the road. Never. I run without my brights because I'd prefer to see the road close to me.
My old car I was able to jumper the fogs to the brights and run all at once. It's a great thing. You can see those tiny rabbits/armadillos crossing the road waiting to destroy your car...

 

Update: I have been working with another forum member and the wiring diagrams on Toyota TIS to pinpoint where and how to do this mod.

As it turns out we were looking in the wrong area. It's not the relays we have to modify, it's the dimmer switch assembly itself. Here is the wiring logic for the dimmer assembly:

The right side shows the signals that the ECU receives from the stalk assembly. What we will have to do is remove the assembly, open it up and solder or tap the control switch to change it to the outcome we want. Will make a writeup on this once I go through with it.

 

waiting patiently with my popcorn for fog light on with DRL (could care less about highbeam+foglight...that's just asking for oncoming cop trouble...since I've sometimes flashed some cops thinking they had their highs on, when it was just those dam new LED headlights they got on their Explorers)

 

Just editorial, and I've restrained myself for a while, but this one always bugs me: Shouldn't that read "...couldn't care less..."?

 

There can't be double negatives in correct English =P (as it was taught in language school) or the point gets negated.

A lot of other languages (like my mother tongue and a few others that I've learned), double negatives emphasize the point that is being put out, but in English, double negative would make it a positive...or something like that.

 

No double negative. Consider what you're trying to say, that your degree of caring is low, so low that it couldn't be lower, ie: you coudn't care less.

I'll leave it at that, way off topic.

 

the test is

I couldn't do less (you did more)
I couldn't love less (you loved more)
I couldn't fish less (you fish too much)
I couldn't see less (you saw more)
etc..
I couldn't care less (you cared more)

the "not" and "less" petty much negate themselves (in correct English). but it is way off topic.

 

I'm waiting for a US spec dimmer assembly to be delivered to me before I can start this mod, but I can tell you what to do. If you look at the wiring diagram I posted you can see that the fog switch (LFG) receives power from the dimmer switch only when it is in low beam position (HL). All you have to do to enable fog lights anytime is connect that LFG wire to the ground wire (EL) instead of HL. Unfortunately this requires removing the steering wheel.

 

Hey guys, I have researched and tested this further and I no longer think it is possible to change the stock fog light setup to work independently of the lowbeams. The logic to control them is not in the dimmer stalk like I initially thought, but in the ECU. There is no way to reprogram the ECU and I don't want to mess around with it because it is an expensive part.

So, I think the only way to achieve fog lights anytime on the Prius C is to install a seperate switch that splices directly to the fog relay. The idea here would be to force the fog relay on regardless of what the ECU is telling it.