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Simple Wiring Diagram to Bypass Foglights (Works w/o Headlights or w/ Highbeams)

43K views 39 replies 15 participants last post by  newkiaowner  
#1 ·
Heres a simple wiring diagram I made to bypass the fog lights. I hated it that i had to turn the foglights on w/ my headlights only or turn off with the high beam on. All you need is one 5-Pin relay and an auxiliary switch.

The wiring diagram


This is where i mounted the relay, closest to the front center. (Ignore the other relays to the right those are for the LED DRls)


Ill post pics of the foglights in operation soon, i realize i didnt have any pics on my phone.
 
#3 ·
I always made 86 my ground cause its like saying "86 the flags" but either way they should work. You are right on the 30 being the power source, but sometimes they need to be switch in order for the relay purpose to work. So far i havent had any problem with that relay. (knock on wood:eek:ccasion14:)
 
#10 ·
Sure thing ill have some pics up but ill have to be in the weekend. The only garage i can work on my car is at work and thats only open in the weekend :duh:


As for tapping in the wires, all i did was cut both foglight bulb sockets w/ at least 2-3ins of wire left on them. Now the fogbulb socket will have 2 wires on each of them, make one ground (-) on each of them and the positive (+)will be power wire coming from the relay. (see diagram on post #1)

Now on the wires you cut the fogbulb sockets from (factory foglight harness) you are left w/ 2 wires on each side. you need to tape up the driver side making it unusable. On the passenger side, find the (+) wire via multimeter and connect it to the relay. tape up the left over wire (-).
On the diagram on post #1, "Factory Fog Harness" is the passenger side (+) wire for the fog lights.

And the rest is just connecting the aux switch from a fuse (any fuse thats live with the engine on only) under the left of the steering wheel.

Im sorry if there isn't any pics yet...
 
#7 ·
Even if you don't have to, it's just easier to take the bumper off and work on it sitting down. I get so frustrated if things don't go my way when I work under the car inside the bumper lol sooo much harder to work that way.
 
#13 ·
The dealership shouldn't even notice unless you tell them.
A Toyota dealer told me once that the 35w HIDs I put on my corolla are going to melt the housing, and charging me $60 per bulb to replace it back to halogens. WTF is that? haha

loman was selling harness for this purpose for $20 last year, I almost got one.
Well here you go, this diagrams on me :)


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#17 ·
Not sure if there is a way to do it like my old car, but I had a 2000 Toyota Celica and we could do it by removing some wires from the relay for the fogs and add a new wire and we had full control of fogs with stock switch on the stalk. Here's a link if someone can figure this out on our cars would be awesome.
http://www.newcelica.org/forums/showthread.php?t=115701


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#18 · (Edited)
Not sure if there is a way to do it like my old car, but I had a 2000 Toyota Celica and we could do it by removing some wires from the relay for the fogs and add a new wire and we had full control of fogs with stock switch on the stalk. Here's a link if someone can figure this out on our cars would be awesome.
Full Control Of Fog Lights (Alternative Way) - pokgai - NewCelica.org Forum


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Our fogs don't have relays. They are switched on/off by the IPS module in the cabin. When the fog switch is turned on, the switch stalk sends a ground signal to the BCM and then the BCM communicates via CANBUS to the IPS which contains outputs for both fog lights. If you wanted to mod the fog lamp circuit to come on when you want and still use the factory switch, you would need to tap into the ground signal wire from the stalk to the BCM and use it to complete the circuit for the coil on a relay.

If you do decide to bypass the IPS module and wire your fogs to a relay, one of the downsides is that you will lose the fog lamp indicator in the instrument cluster.
 
#19 ·
Heres a simple wiring diagram I made to bypass the fog lights. I hated it that i had to turn the foglights on w/ my headlights only or turn off with the high beam on. All you need is one 5-Pin relay and an auxiliary switch.

The wiring diagram
View attachment 15418

This is where i mounted the relay, closest to the front center. (Ignore the other relays to the right those are for the LED DRls)
View attachment 15419

Ill post pics of the foglights in operation soon, i realize i didnt have any pics on my phone.

I would check your relay to see how much holding current it is rated for. You probably need to bias the inductor with some type of voltage divider.
 
#20 ·
In my old car (240sx) I wired the factory fog lights to my sidemarkers aka parklights (that don't blink with turn signal) so that way when I turned on my parking lights with the headlights off my fogs light up.. Still just as bright as before and everything.. Not sure about the light on the dash tho mine didn't have one. But it was a very easy mod to do. Just make sure with any wiring done that you seal up all bare wire connections to insure no bad connections or corrison later on in life... This may or may not help with our optimas'? Just figured i'd throw my 2 cents in there also... Plus where are these pics?????????
 
#23 ·
There are no pros to wiring it in series and likewise, there are no cons to wiring in parallel. In a parallel circuit, current is divided and voltage is constant. In a series circuit, voltage is divided and current is constant. I'll see if I can draw up a crude diagram to make it easier to see.
 
#24 · (Edited)

In the series circuit both resistors have the same current. In this example the current is 1.2mA. Since there are 2 resistor of equal value, they divide the voltage applied equally. With 12 volts applied, each resistor drops 6V. If the resistors were different values, they would drop different voltages based on their value. Both voltage drops must equal the voltage applied(Kirchoff's Voltage Law). While the voltage is divided between the two resistor, the current of 1.2mA is constant in both.

In the parallel circuit all three resistors see 12 volts. The current is divided between the 3 resistors. Because the resistor values are all the same, each leg of the circuit will have the same current flow. If the resistor values were different each leg would have a different current flow. In this example, the current flow is 2.4mA in each leg. In a parallel circuit all resistor values need to be converted to their inverse and added together and then converted to the inverse of the totals. In this example all resistors are 5K ohms. The inverse of 5000 is 0.0002. 0.0002 x 3 = 0.0006 The inverse of 0.0006 is 1666.7. So, the total resistance of the parallel circuit is 1667 ohms. That makes the total circuit current 7.2mA. Tje current in all legs of a parallel circuit must equal the current calculated by finding the inverse totals and applying Ohm's Law.

Here are the 12 versions of Ohm's Law where V=voltage I=current P=power and R=resistance:
voltage = volts current = amps power = watts resistance = ohms

V = square root of (P x R)
V = P/I
V = (I x R)

P = V squared/ R
P = (I squared x R)
P= (I x V)

I = V/R
I = P/V
I = square root of P/R

R = p/(I squared)
R = v squared/ P
R = V/I
 
#33 ·
Bah, was reading through this thread and just when the technical info was pouring out, BAM - emotional breakdown!

071K or the OP - Would you all know of a product already on the market that would allow an LED curcuit to slowly power on - STAY ON, then when switched off, slowly power down.

Maybe some sort of controller with Capacitors or some sort of active resistor circuitry??? Ideas?
 
#34 ·
I know what your talking about, I have my LED door handles turn off slowly like the dome lights. I just tapped into the dome lights tho. But observing from my volt meter in order to get the lights to dim, the volts would drop from 12v slowly down to 0v. Im pretty sure theres something out there for this purpose but I dont know what its called sorry