if i tap into my headlights to power my fogs will it dim my headlights? the reason i want to do this is so my fog lights will go off when i turn my brights on.

 

if you used your head lights to trigger a relay, and then use power from your battery, that way when your highs go on the relay cuts out sense the relay trigger doesnt have power anymore. I just be very careful with this type of wiring, if your not you could hurt yourself should your wiring fail and you headlights stop working while driving down a dark road.

 

don't have much experience using relays. any body have a right up? part number? pic or diagram?

 

Hope this can be of help.

A relay is nothing but a switch using a small current to control a big one, this removes the necessity of running large amounts of electricity through something like your steering column when the headlights are on.

The relay you will need is called a normally open relay, this means that whenever there is no power to the relay itself it disconnects power to whatever your controlling in this case your fog lamps.

Now, within the relay there are 2 circuits, the control circuit and the component circuit. If you go to a parts store they have a square relay, looks just like this [attach. 1] but 4 pins.

On the bottom of the relay you will see 4 prongs, each of these prongs will have a corresponding number: 84&85, 87&30. these are to help distinguish which go where. The relay closes when you close your control switch, it energizes a little coil inside the relay that looks like the pigtail in attach #2 and closes the component switch allowing electricity to flow from the battery to the foglamps.

Now using attach. #2 you can see how there is a control circuit 85-86 and the component circuit 87-30. Using this diagram you can wire up your own relay to control the fog lamps.
As said before me, it would probably be a lot safer and smarter than tapping into 25 year old wire to simply run a switch into the cabin and control the relay yourself, this is so you keep your circuits completely separate and if you lose one, you have the other just in case.

If it's still confusing I would suggest a bit more searching using the keyword relay to see if someone has made a more thorough write up maybe controlling a fan or something.

 

I have my driving lights connected to a switch on the dash. They are also connected to the high beams. Anytime the switch on the dash is turned on the driving lights turn on. If the switch on the dash is turned off the driving lights turn off, except...When the high beams are turned on the driving lights come on. When the high beams are turned off the driving lights turn off also.

I used a relay also but different wiring. Nice diagram. I stole it.
There are three wires in the headlight plug. Black is ground. Red/yellow has 12v when low beams are on. Red/blue has 12v when high beams are on. You can tap into the Red/blue wire near the plug on the back of the left headlight and install the relay in front of the battery.

 

I did the same installing my halogens; manual switch controlling a relay.

Switch side of relay draws from the accessory line under the dash.

Power side taps power from the inlet screw on the main fusible link block, via it's own dedicated fuse. ALWAYS fuse your power lead as close as possible to your source of power.

I mounted the relay against the front bulkhead just behind driver-side headlight, so all the high-current runs are short, and I only had to pull a single small-gauge wire into the cabin.

Works slick and looks very professional, IIDSSM.



I used a standard relay with a socket, so any failures in future would be easy to replace.

Not shown in the pic, but I used rubber splicing tape to boot the bottom of the relay & make it waterproof.

 

so would any of these in the link work or do i need a specific one?

relays at autozone

 

Where'd you buy your relay? got a part #?

 

It's a pretty standard 30-amp 12VDC SPDT relay, from Bosch. I had it for a long time before I used it - - another one of those projects that you buy all the stuff for, then don't actually do for 7 or 8 years, heh.

I believe I've seen them or similar ones at Autozone, though I got mine through an electronics supply house that I visit a lot.

I'll jot down the Bosch part number off the top of it tonight.

 

I was remembering wrong -- not a Bosch part, a Siemens part: VF4-45F11

Datasheet for the Tyco equivalent is here:

http://www.mouser.com/ProductDetail/...252bhUcA%3d%3d

 

Don't buy a shitty Chinese made relay. In a moist climate a non sealed or incorrectly sealed relay will fail. Use a good quality automotive relay such as that made by Bosch, Tyco, Siemens, AMP, Panasonic or the like.

Fog lights should not be on if you have high beams on. Wire the relay as follows:
85 to the Red/Yellow wire in the headlight plug (+12V when lowbeams are on).
86 through the firewall (make sure to use a grommet) to one terminal of your switch. Wire the other end of the switch to ground.
30 to a fused 12V source (try tapping in to where the positive battery cable screws to the fusible link block)
87 to your fog lights.

This configuration is the correct operation for fog lights (same function as OEM manufacturers use). It allows your fog lights to be controlled with a switch, but only come on when your lights are on. It also prevents you from leaving them on and draining your battery. In addition it turns them off if you turn on your high beams, as fog lights are useless when used with high beams.

http://www.easternbeaver.com/Main/El...ys/relays.html has really nice relays, Japanese made and sealed. They also sell connectors to make a professional job out of it.

 

Ok I think I understand how to wire the relay but how's the switch gonna be wired now?

 

The switch just allows a path to ground from the coil of the relay. One side of the switch to pin 86 on the relay, the other side to chassis ground.

 

So basically the way I've got it wired now minus the wire to the fog lights. That's what I thought just wanted to make sure.

 

Ok what'd I do wrong? The fog lights come on and go off with the headlights but they don't go off when I flip the switch or when I turn on my high beams.

 

So you have your +12VDC from the low beam connected to pin 85, providing power to the coil only when you have your low beams on.

One end of your switch is connected to pin 86, and when closed, the switch allows some current from the low beam circuit to flow through the coil of the relay, through the switch and to ground. If the switch is open, current cannot travel to ground, and thus there is no current through the relay coil.

Pin 30 of the relay should be connected through a fuse to a constant 12VDC source on the car, perhaps near the main fusible link.

Pin 87 should go to the fog light. When current is running though the coil, (lowbeams are on and switch is closed), the electromagnetic force of the coil should complete the circuit from pin 30 to pin 87.

Here are some things to check.

• If you connect 12vdc to pin 85 and ground pin 86 does the circuit from pin 30 to 87 close?
• If you remove the wire from pin 86, do the lights come on ( they shouldn't)
• If you remove the wire from pin 85 do the lights come on?
• If the lights come on only when the lowbeams are on and pin 86 is shorted to ground, check the switch for correct operation.
• Does the red/yellow wire only have +12VDC when the low beams are on.

We'll get this sorted out for you.

 

Well I used a relay for an electric fan could that be the problem? I'll have to retrace all my wires and make sure everything right. Probably be Friday though cuz I gotta put a cd player in my wires 3000gt vr4 which requires removing half the dash. And she thinks I'm jelouse of her awd and 300 hp. By the way can you show me a diagram of how the ground and the wire from the relay are supposed to be plugged into the switch? I have the wire from the relay to the prong numbered 1 and the ground into number 3.

 

Do you have a multimeter? I can't tell you which prongs on the switch without testing it as there are so many different types.

 

Terrific information Sarge!
This should be archived!

 

Don't have a multimeter unfortunately but I do have one of those cheap little testers that has the light bulb inside it. Will that work?

 

We can make it work... do you have a Harbour Freight in your town? A multimeter is a tool that will pay for itself many times over. You don't need a 500$ Fluke meter like mine, a 5$ harbour freight will work for this.

 

Never heard of harbour freight but I bought a multimeter at walmart last night for like 10 bucks

 

We used multimeters a few times in wheeled vehicle mechanics training for the army but I might need a refresher course.

 

I'm assuming I need to test each wire to see which one is only hot when the headlights are on?

 

First lets check if the red/yellow wire only has 12VDC when the low beams are on. Use the DC Volts mode of the multimeter.