Electrical Gurus... a quick question

tj!2k4 · 03-27-2006, 04:24 PM

Quick question for the electrical gurus:

I want to wire my fogs up so that they turn on independent of the head/parking lights, but only when the ignition is turned on. Right now, at least the parking lights have to be on before the fogs turn on.

My theory is to tap into the power from the defroster switch, which only receives power when the ignition is on.

There's a bunch of info (such as plug color and and wire location that you won't care about, but which will help me remember what is what).

Fog Light Switch (purple plug):
grey wire (2nd-from-top) switched on/off w/ headlights
ca. 11.5V

Defroster Switch (brown plug):
pink/blue (top) switched w/ ignition
ca. 11.9V

--> Jumper from grey wire on purple plug (fog) to pink/blue on brown plug (defroster).

Aside from the slight voltage discrepancy, which shouldn't make a difference, does anyone see a problem with this?

TIA

Das · 03-27-2006, 05:05 PM

This is what I got.

tj!2k4 · 03-27-2006, 05:16 PM

thanks.. they're the stock fogs in an 03 Mustang GT, so all the wiring is already there.

I just need to know if there's some kind of electrical faux-pas I'd be committing by jumping the power wires.

nice car, btw.. 67 Malibu.. drooooool

Das · 03-27-2006, 05:30 PM

Oh ****, I forgot, the other line off of the relay would go to the switch, either the stock switch, or a custom switch.

Thank you, I wish she was running right now, I blew up the transmission and I dont have the money to rebuild it right now.

www.osshole.com/images/

Her name is Delila

tj!2k4 · 03-27-2006, 06:22 PM

Well fortunately I'm quite the adventurous fellow, so I decided to give it a shot:

The good news is that nothing blew up, and it does make the fogs turn on and off independent of the headlight switch.

However, the parking lights are permanently on when power is applied to the grey wire.

Oh well. Nothing lost, nothing gained, except a bit of knowledge.

bgoodman · 03-27-2006, 07:57 PM

I'm just curious as to WHY you want the fogs to be operable seperately?

tj!2k4 · 03-27-2006, 08:37 PM

Because although they're supposed to be fog lights.. they actually don't really provide any additional lighting, especially not in the fog. They're actually more like DRLs.

Basically they're just lights that say "Hey, I'm a GT" as opposed to a V6, and they make the car look a tad nicer when they're on.

Specimen · 03-27-2006, 08:55 PM

I have a friend who did a similar thing where he wired a rear cam through a 12v swtich and used the power from the reverse lights to turn on the camera when in reverse. Now when he turns on the camera through the switch, the reverse lights come on even though he’s not in reverse.

Does your defroster come on now when you turn on your lights?

tj!2k4 · 03-27-2006, 08:58 PM

ha, that's funny.. but no, i just tapped the + power from the defroster switch.

Apparently the "fog" switch is wired in such a way that the parking lights turn on when the "fogs" turn on. And I undid the wiring as soon as I saw that the parking lights come one. The whole point of this exercise is to run the "fogs" like daytime running lights.

Specimen · 03-27-2006, 09:52 PM

Did you just tap into the grey wire, or did you cut it and connect the defroster +12v to where the grey wire connects to the purple plug (fog switch). If you just tapped it, any power that you are applying to that grey wire will go through the fog switch and also back through the other direction on the grey wire. Now since your fog lights ONLY come on when your parking lights are on, that means your grey wire is only hot when you turn on the parking lights. Since you are now making that grey line hot the parking lights have to be on.

Specimen · 03-27-2006, 10:08 PM

I bet if you hook it back up how you had it, your parking lights will be on whenever your keys are in the ignition. Regardless if your fog light switch is on or off. If this is the case all you probably have to do is cut that grey wire just before you made that tap. This will force the +12V from the defroster to only travel through the fog switch (purple plug) then to your fog lights and not through the grey wire in the opposite direction towards the parking lights. Also remember to cover than grey wire after you cut it to prevent it from touching ground. If you don’t then when you turn on your parking lights, you’ll blow fuses.

DK888 · 03-27-2006, 10:14 PM

I can give you a hand this weekend...but it better not get in the way of the korean bbq. lol

tj!2k4 · 03-27-2006, 10:33 PM

I just tapped into the grey wire, didn't cut anything. I'm always afraid to cut things.. :dunno:

Quote: Originally Posted by Specimen

I bet if you hook it back up how you had it, your parking lights will be on whenever your keys are in the ignition. Regardless if your fog light switch is on or off.

That is correct

Quote: Originally Posted by Specimen

If this is the case all you probably have to do is cut that grey wire just before you made that tap. This will force the +12V from the defroster to only travel through the fog switch (purple plug) then to your fog lights and not through the grey wire in the opposite direction towards the parking lights. Also remember to cover than grey wire after you cut it to prevent it from touching ground. If you don’t then when you turn on your parking lights, you’ll blow fuses.

Oh, I see what you're saying.. good idea. I didn't think about the current also flowing back towards the parking lights. Hmm. Thanks for the tip, I just may have to try that tomorrow. Thanks again!

tj!2k4 · 03-27-2006, 10:34 PM

Quote: Originally Posted by DK888

I can give you a hand this weekend...but it better not get in the way of the korean bbq. lol

Don't worry, there is nothing that could possibly get in the way of that tasty BBQ goodness!

kamikaze2112 · 03-27-2006, 10:57 PM

i haven't really got a good visual in my head of what is goin on, but you can use a diode to prevent the current flow back into the parking lamp circut. I have a manual switch to 'fake' the ACC lead on my M2ATX, which is also connected to the radio fuse. whenever the manual switch was on, the radio and other power accessories would stay on. I fixed this by putting a diode in line with the power line coming from the radio fuse in the fusebox, to allow current to flow only to the M2ATX and not backwards back into the Power accessories

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