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How to Make Fog Lamps Come on w/Low Beams?

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Old 11-16-2015, 03:59 PM
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How to Make Fog Lamps Come on w/Low Beams?

Hello - I just acquired some auxiliary lights for my 94 Toyota 4x4 and I'm trying to wire them up as fog lamps. The wiring harness (w/relay, etc) is properly installed and in place. I want them to come on automatically with my low beams, and off with my high beams. The problem is that my ole 94 has no fuse for hi and lo beam for me to attach to. Well, not that I can locate. Can someone help me out?
Old 11-16-2015, 04:09 PM
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Unless you live in Canada, there is no fuse or relay for the high/low function. It goes straight through the switch on the stalk.

But this wiring is quite trivial; you just splice into one of the wires to a headlamp, and use that to trigger your relay.

You ought to be aware that many "fog lamps" are illegal unless they have the same upper-edge cutoff as regular low beams, so as to avoid blinding oncoming drivers. (And they can only be used with the regular low beams, but you already figured that out.)

Some states make it illegal to use fog lamps in the absence of fog, so hard-wiring them to the headlamps may not be what you want to do.
Old 11-16-2015, 04:14 PM
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Originally Posted by scope103
Some states make it illegal to use fog lamps in the absence of fog, so hard-wiring them to the headlamps may not be what you want to do.
i wish ALL states would not only make it illegal to use them in the absence of fog, but would enforce such a law, too.
Old 11-16-2015, 04:42 PM
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Originally Posted by scope103
you just splice into one of the wires to a headlamp, and use that to trigger your relay.
First, thank you for responding to my post! What you describe here is exactly what I did. But here's what happens; When I initially turn my headlights on, the fog lights come on. And when I switch to high beams, the fog lights turn off. All's good so far, right? But when I switch back to low beams the fog lights DO NOT come back on. They stay off.

Originally Posted by scope103
You ought to be aware that many "fog lamps" are illegal unless they have the same upper-edge cutoff as regular low beams, so as to avoid blinding oncoming drivers.
Yes, I am aware of this. I'm not trying to blind anyone, so I've adjusted them accordingly.
Old 11-16-2015, 04:45 PM
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Originally Posted by wallytoo
i wish ALL states would not only make it illegal to use them in the absence of fog, but would enforce such a law, too.
I guess we differ on that. I live in a location where there's lots of fog in the winter and it's also rural so wildlife is often in the road. I want as much light as possible so I can see any danger and avoid it, fog or no fog.
Old 11-16-2015, 06:34 PM
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Then you have a wiring problem. Put your multimeter on the control line of your relay and watch the voltage. I'll bet you've got a big resistance in your wiring somewhere, so the relay just BARELY works.
Old 11-16-2015, 11:52 PM
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Red face

Without knowing just how you wired this up .

Pretty hard to trouble shoot your problem.

The same can be said about lifted trucks with head lights not adjusted that always seem to tail gate me in the dark.

Yes some of those fines for hitting a deer can be quite expensive
Old 11-17-2015, 01:55 AM
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Originally Posted by Brock Lee
What you describe here is exactly what I did. But here's what happens; When I initially turn my headlights on, the fog lights come on. And when I switch to high beams, the fog lights turn off. All's good so far, right? But when I switch back to low beams the fog lights DO NOT come back on. They stay off.
1994 model trucks and 4Runners may still have switched ground control for headlights. If that is so, merely tapping positive of relay coil to positive side of low-beam beam wire and grounding the other side of relay coil will not work.
To simplify your wiring BUT STILL MAKE IT WORK LIKE YOU ORIGINALLY WANT:
(1) Tap positive side of relay coil to positive side of low-beam filament, and
(2) Tap negative side of relay coil negative side of low-beam filament
Do this very close to the bulb connector to be exactly sure of the wires.

However, best if you posted (1) schematic of your truck, and (2) schematic of your fog light kit so we can pinpoint exactly where to tap off of.
Old 11-17-2015, 06:44 AM
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Originally Posted by RAD4Runner
1994 model trucks and 4Runners may still have switched ground control for headlights. If that is so, merely tapping positive of relay coil to positive side of low-beam beam wire and grounding the other side of relay coil will not work.
To simplify your wiring BUT STILL MAKE IT WORK LIKE YOU ORIGINALLY WANT:
(1) Tap positive side of relay coil to positive side of low-beam filament, and
(2) Tap negative side of relay coil negative side of low-beam filament
Do this very close to the bulb connector to be exactly sure of the wires.

However, best if you posted (1) schematic of your truck, and (2) schematic of your fog light kit so we can pinpoint exactly where to tap off of.
Dude! You always have great info, I plan on doing this one my 4Runner
Old 11-17-2015, 08:43 AM
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Originally Posted by RAD4Runner
1994 model trucks and 4Runners may still have switched ground control for headlights. If that is so, merely tapping positive of relay coil to positive side of low-beam beam wire and grounding the other side of relay coil will not work.
To simplify your wiring BUT STILL MAKE IT WORK LIKE YOU ORIGINALLY WANT:
(1) Tap positive side of relay coil to positive side of low-beam filament, and
(2) Tap negative side of relay coil negative side of low-beam filament
Do this very close to the bulb connector to be exactly sure of the wires.

However, best if you posted (1) schematic of your truck, and (2) schematic of your fog light kit so we can pinpoint exactly where to tap off of.
Thank you for your help with this! I gotta admit, I don't understand everything you wrote though. Here's how the lights are installed:




My fusebox contains a relay for the headlights and a fuse for each the left and right headlights. Headlights have 3 wires to 'em. Per the wiring diagram wire 86 is connected to the low beam wire. But, as I noted, the fog lights aren't doing what I want them to do. Can you shed some "light" on this for me? Pun intended. :-)
Old 11-17-2015, 08:44 AM
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I would have rather sourced an oem fog light switch, and wired them separately on their own relay, drawing switched power from the marker light circuit so they will work only when marker lights are on.

This gives the ability to run fogs only, without any headlights. When you're in real thick fog, you want only the lowest mounted lights on to minimize the glare. It also prevents leaving them on by mistake as they will turn off when you switch off markers. But they will operate with high beams for when you need max light. This provides the most flexibility but includes the ability to switch off all from the lever.

In the diagram above, run 86 to corner marker.
Something to consider is all.

Pardon me for side bar rant:
Why, why, why, must people put on their little policeman hat to express opinions about what is illegal? Not only is legality varying by state and country, it's also completely irrelevant for off road only vehicles, and there are no shortage of those in this forum. Speeding, failing to signal, dark window tint, all possibly illegal, yet no reason to warn people about any of these with each post made either. Just answer a man's question and leave the condescending warning out. Sorry, just irritating.
/rant

Last edited by tj884Rdlx; 11-17-2015 at 08:59 AM.
Old 11-17-2015, 08:49 AM
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Originally Posted by RAD4Runner
To simplify your wiring BUT STILL MAKE IT WORK LIKE YOU ORIGINALLY WANT:
(1) Tap positive side of relay coil to positive side of low-beam filament, and
(2) Tap negative side of relay coil negative side of low-beam filament
Do this very close to the bulb connector to be exactly sure of the wires.
If we're talking about the 3 wires that connect to the headlight I don't know which wires are positive and negative of low-beam filament. I do know that when I connect to one of them my lights are always on. Perhaps that's the positive? Each of the other two wires seem to be reserved for low beam and high beam respectively.

Originally Posted by RAD4Runner
best if you posted (1) schematic of your truck
Don't know how to do that or where to get it.
Old 11-17-2015, 08:52 AM
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Originally Posted by tj884Rdlx
I would have rather sourced an oem fog light switch, and wired them separately on their own relay, drawing switched power from the marker light circuit so they will work only when marker lights are on.

This gives the ability to run fogs only, without headlights. When you're in real thick fog, you want only the lowest mounted lights on to minimize the glare. It also prevents leaving them in by mistake as they will turn off when you switch off markers.

Something to consider is all.
I hear ya. But I don't want another switch if I can avoid it. And I don't want to accidentally leave lights on. I want the best of both worlds; I want the lights to read my mind and KNOW when I want them on and when I want them off. :-)
Old 11-17-2015, 10:00 AM
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Originally Posted by dropzone
Dude! You always have great info, I plan on doing this one my 4Runner
Thanks, Robb.

Originally Posted by tj884Rdlx
I would have rather sourced an oem fog light switch, and wired them separately on their own relay, drawing switched power from the marker light circuit so they will work only when marker lights are on.
This is how I would do mine, too.

Originally Posted by Brock Lee
... I want them to come on automatically with my low beams, and off with my high beams.
Thanks for the diagram. For now, I suggest you disconnect everything you did to be safe.

Originally Posted by Brock Lee
If we're talking about the 3 wires that connect to the headlight I don't know which wires are positive and negative of low-beam filament. Don't know how to do that or where to get it.
There should be schematic somewhere online, but in order to be thorough and be sure, pls post picture of back and front of your headlight connector (I have a 1985 first-gen, so not sure about your 1994) showing clearly wire colors.
I'll show you how to verify wiring, and where to connect everything once that's done.
Old 11-17-2015, 11:37 AM
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OK, found schematic for 1990-1995 4Runner. Should be the same.
Here's your circuit:
Before you do anything, probe pins 2 and 3 make sure there is 12V across them when, and only when, low-beams are on.
You can disconnect connector from bulb in order to prove for voltage. positive (red) probe on 3, negative (black) probe on 2

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Old 11-17-2015, 01:11 PM
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Originally Posted by RAD4Runner
OK, found schematic for 1990-1995 4Runner. Should be the same.
Thank you! I appreciate the help like you don't know. I'll try it tonight and let you know the results. Yes, my wires are those colors as your schematic points out.
Old 11-17-2015, 02:26 PM
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Cool. Most welcome. pls keep us posted.
Old 11-17-2015, 03:46 PM
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ray is an excellent resource. especially for electricity.

wally
Old 11-18-2015, 08:57 AM
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Originally Posted by RAD4Runner
Cool. Most welcome. pls keep us posted.
I didn't get a chance to fiddle with my lights last night. But as soon as I get a chance, I will let you know the results. I promise.
Old 11-18-2015, 06:32 PM
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Originally Posted by RAD4Runner
pls keep us posted.
No dice. But my wires are the same colors as in the schematic you provided. I hooked up the relay and everything like your image indicated. Here's what happens; The fog lights come on with my headlights and turn off with my headlights, but they stay on during low beam and high beam.

I think I noticed something; Once I turn on my head lamps the low beams seem to stay on even while the high beams are switched on. And one of the wires always seems to be energized. I'm guessing that's the red/black.

Perhaps if I just connected 86 to red/green and 85 to red/black? Would that yield the results I want? I don't know. I'm just playing with wires here.


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