Wire fog lights to come on with parking lights?

[donkitchen]

Does anybody know of a way to wire up or modify the fog lights so that they can come on with the parking lights vs. only the head lights? I did some searching and didn't come up with a thread that previously discussed this. If there is one my apologies, please point me in that direction.

[wls]

look under fog lights retrofit fog light on 2010 prius. just tap in the wire from you relay that turn on the fog lights to your parking light,so went you turn on the parking lights them fog lights will go on.

[donkitchen]

After looking at that thread it seems mostly geared at people adding fog lights to non Model Vs. I am a V owner with existing OEM fogs. Your suggestion seems to make sense but I'm curious if anybody has done this at all or can provide a specific example. I'm not too confident in jumping fuses on my own so I may just forget about it if nobody has done it.

[chrisj428]

If I could speak for Don a moment, what I think he (and I) would like to do is be able to turn the foglights on when just the parking lights are on.

Right now, the way the lights are wired, the foglights will only come on when the headlights are on, defeating the intended purpose of the foglights altogether.

[donkitchen]

Exactly!

Originally Posted by chrisj428

If I could speak for Don a moment, what I think he (and I) would like to do is be able to turn the foglights on when just the parking lights are on.

Right now, the way the lights are wired, the foglights will only come on when the headlights are on, defeating the intended purpose of the foglights altogether.

[jayvee]

Originally Posted by donkitchen

Exactly!

Sorry, I hope I'm misunderstanding. You want to drive around in the fog with only fog lights and parking lights? If visibility is reduced due to fog, you are generally supposed to have the headlights on. (But I don't know your states' laws...) And if you're getting excessive glare in fog with your low beams, they may not be aligned correctly. Fog lights are intended to supplement low beams toward the sides and a short distance in front of the vehicle. If it's foggy, I want to see your low beams coming toward me, not just fogs and parking lights...

But if you really want to do this, I think you can wire a separate switch that provides the ground path for the fog light relay, using the tail (parking) light switch position:

Connect a switch between the following two pins of L47, which is the connector that goes into the bottom of the headlight switch stalk. (You'll need to remove the bottom steering wheel cover to do this. There are instructions here: Fog Lights: Install [Retrofit] fog lights on 2010 Prius?)

Connect a switch betwen these two wires of L47.
Pin 4 - Light Green (Fog)
Pin 18 - Yellow (Parking light)

When this switch is closed and you turn on the parking lights, the fogs will come on as well. However, it also means that if you have this new switch "On" and turn on the fog light switch, it will also turn on the parking lights. This is by far the simplest solution, if you can live with them being "joined" this way.

Before you tap into the wires, I would try this with a small jumper wire stuck into the back (wire) side of the connector pins, to make sure the ECU isn't applying some other logic to the control relays. I don't think it is, though.

Hope this works for you! And I hope I'm not driving near you in fog!

[chrisj428]

Jay,

There is much misunderstanding re: foglight operation in the USA.

Heck, just about every Audi, Volvo, Jaguar and MB I've driven behind as of late is running their rear fogs on during a clear night...something which would be a ticketable offense in Europe.

In Europe, it is expected that, in fog, you drive with foglights. Low beam headlights have too much throwback from their beam pattern. Subsequently, when designed properly, the fog lights are to be the primary source of illumination in fog. With a proper set up, fog lights should operate with parking/marker lights and independently of low beam operation.

[jayvee]

Originally Posted by chrisj428

Jay,

There is much misunderstanding re: foglight operation in the USA.

Heck, just about every Audi, Volvo, Jaguar and MB I've driven behind as of late is running their rear fogs on during a clear night...something which would be a ticketable offense in Europe.

OK, but I think we're talking about front fogs here, aren't we? There are no rear fogs on the US Prius.

In Europe, it is expected that, in fog, you drive with foglights. Low beam headlights have too much throwback from their beam pattern. Subsequently, when designed properly, the fog lights are to be the primary source of illumination in fog. With a proper set up, fog lights should operate with parking/marker lights and independently of low beam operation.

Understood - I'm not familiar with European regulations. However, in most US states, as far as I know, fogs are considered "auxiliary lighting", and therefore are supplemental to primary headlights (low beams). Laws regarding required lighting under reduced visibility refer to primary headlights, not auxiliary lighting (since not all vehicles have them). It may be true that under a properly designed low beam and fog system, you could only use fogs. However, I don't think that assumption applies to most vehicles. In addition, the beam pattern for fogs is so low and drops so rapidly that your visibility to other drivers is significantly reduced if you only use fogs. That was my point.

But hey - it's just my opinion, and if I wanted to police you, I wouldn't have provided the info.

[ilusnforc]

My roommate has a Ford Ranger (somewhere around '00-'02 model) that came stock with foglights and he can turn the fog lights on/off while just the parking lights are on. The user Darelldd on these forums has instructions to wire the foglights to be able to turn on/off anytime for the Gen II Prius which I have, but have yet to perform the mod although I'd like to and for a long time have been meaning to. Very simple, just 2 wire splices and a diode. His site is:
Darell's Electric Vehicle Page

[chrisj428]

Originally Posted by jayvee

But hey - it's just my opinion, and if I wanted to police you, I wouldn't have provided the info.

I hear ya, Jay! No hard feelings at this end at all. I guess what OP and I are looking for is a way to give us the option.