Fog light wiring
06-04-12, 09:21 PM
#1
Fog light wiring
Read this in another post on wiring the fog lights in an S4:
"This is just a guess but you could use a 5 pin relay with two 87 pinis. They have these in the auto parts store in the headlight and fog light section where I'm at.
Run a ground wire from the chassis to one end of the fog light switch, the other end from the switch to pin 86 on the relay.
Pin 85 would be go to a place that supply 12v when the key is turned to the on position
Pin 30 would connect to the battery (be sure to wire in a fuse, no idea what size maybe 30amp)
Pin 87 and 87 would connect to each fog light.
The ground wire on the fog lights will ground somewhere to the chassis
This way when you flip the fog light switch it kicks on the relay and provides power to the lights.
That should be it, just remember the 5 pin relay has two 87 pins, not 87 and 87A."
According to the post, you're not supposed to use a relay with an 87 and 87a pin. Does this also correlate to the pin layout in the stock 5 pin relays in the car? They're labeled as NO, NO, COM, COIL, and COIL so I'm not sure where it wires to exactly. IE 30, 85, 86, 87, possibly 87a. this is for wiring the lights independently to the headlights, as opposed to only being able to have them on when the headlights are on.
"This is just a guess but you could use a 5 pin relay with two 87 pinis. They have these in the auto parts store in the headlight and fog light section where I'm at.
Run a ground wire from the chassis to one end of the fog light switch, the other end from the switch to pin 86 on the relay.
Pin 85 would be go to a place that supply 12v when the key is turned to the on position
Pin 30 would connect to the battery (be sure to wire in a fuse, no idea what size maybe 30amp)
Pin 87 and 87 would connect to each fog light.
The ground wire on the fog lights will ground somewhere to the chassis
This way when you flip the fog light switch it kicks on the relay and provides power to the lights.
That should be it, just remember the 5 pin relay has two 87 pins, not 87 and 87A."
According to the post, you're not supposed to use a relay with an 87 and 87a pin. Does this also correlate to the pin layout in the stock 5 pin relays in the car? They're labeled as NO, NO, COM, COIL, and COIL so I'm not sure where it wires to exactly. IE 30, 85, 86, 87, possibly 87a. this is for wiring the lights independently to the headlights, as opposed to only being able to have them on when the headlights are on.
06-04-12, 10:01 PM
#2
No.
Just no.
A standard 4 pin NO (normally open) relay is all you need, there is no need to hypercomplicate this.
This sort of relay is the basic building block of an electrical system, it will behoove you to learn how it works.
And I am just the sort of pedantic SOB to learn ya.
Think of the relay as two separate circuits...one feeds power, the other controls it.
Pins 85 and 86 are the control ("coil") side, 30 and 87, the power.
A relay is not polarity sensitive, you can reverse the two contacts of each pair and it will still work.
A fused 12v supply goes to pin 30 (or 87) and pin 87 (or 30) goes to the device (your fog lights).
Pin 85 (or 86) goes to ground, pin 86 (or 85) goes to a switched +12v.
You have all sorts of options with the control side of the relay.
It requires very little current to operate, so the wires need not be as robust as the power handling side of the relay. On some relays the contacts for the coil (control side) are smaller than the other two but usually not. Sometimes they are different colors...on the Toyota relays the power contacts are copper and the coil contacts are silver...but most have the pins marked with the numbers.
It's usually easier to put your switch on the ground side of the coil pair, that way you're only running one wire into the cabin, but it doesn't matter, you can put it on the power side if you like.
Just no.
A standard 4 pin NO (normally open) relay is all you need, there is no need to hypercomplicate this.
This sort of relay is the basic building block of an electrical system, it will behoove you to learn how it works.
And I am just the sort of pedantic SOB to learn ya.
Think of the relay as two separate circuits...one feeds power, the other controls it.
Pins 85 and 86 are the control ("coil") side, 30 and 87, the power.
A relay is not polarity sensitive, you can reverse the two contacts of each pair and it will still work.
A fused 12v supply goes to pin 30 (or 87) and pin 87 (or 30) goes to the device (your fog lights).
Pin 85 (or 86) goes to ground, pin 86 (or 85) goes to a switched +12v.
You have all sorts of options with the control side of the relay.
It requires very little current to operate, so the wires need not be as robust as the power handling side of the relay. On some relays the contacts for the coil (control side) are smaller than the other two but usually not. Sometimes they are different colors...on the Toyota relays the power contacts are copper and the coil contacts are silver...but most have the pins marked with the numbers.
It's usually easier to put your switch on the ground side of the coil pair, that way you're only running one wire into the cabin, but it doesn't matter, you can put it on the power side if you like.
06-05-12, 04:58 AM
#4
Junior Member
Join Date: May 2006
Location: Brisbane, Australia
Posts: 30
Likes: 0
Received 0 Likes
on
0 Posts
Yes that will work, as a general rule of thumb though 87 is your output and 30 is your input, so 87 should go to your lights.
For the other side of your switch I would grab a park light feed so that you dont accidentally switch on your switch and drain your battery when the car is off, your fog lights will only work with your park, high and low beam though
Clokker your technically correct but technically wrong, I always run the earth to pin 85, on a resistor protected relay it doesn't matter but on a diode protected relay it has to be 85 so best to run with pin 85 for earth
Cheers
For the other side of your switch I would grab a park light feed so that you dont accidentally switch on your switch and drain your battery when the car is off, your fog lights will only work with your park, high and low beam though
Clokker your technically correct but technically wrong, I always run the earth to pin 85, on a resistor protected relay it doesn't matter but on a diode protected relay it has to be 85 so best to run with pin 85 for earth
Cheers
06-05-12, 02:49 PM
#6
Stephen16, the other side of the switch should go to the parking lights? Apologies for the noob question but what color and where is that wire. Looking for a general idea before I run and waste a bunch of wire.
Again, just to clarify:
pin 87 -> light
pin 30 -> fuse -> +12v battery
much thanks to both of you.
Again, just to clarify:
pin 87 -> light
pin 30 -> fuse -> +12v battery
much thanks to both of you.
Thread
Thread Starter
Forum
Replies
Last Post
