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Aux light wiring with 3 position switch

Discussion in 'The Garage' started by Skigirl, Jan 25, 2003.

  1. Skigirl

    Skigirl 1/2 ton status

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    Found a site Relay Wiring that details how to wire lights to work either automatically with high or low beams, or independently, when a ON-OFF-ON switch is used.

    My confusion is this: The author of this article spec'd the wire gauges to be used in his first diagram:
    [​IMG]

    Then, when diagramming the 3 position switch, he uses an 18 gauge wire spliced to the 20 amp fused power wire going to terminal 30 on the relay:
    [​IMG]

    Seems to me that the 18 gauge wire going to that switch has 1) too small a wire and 2) too much current for the switch, uless the switch itself is rated for 20-30 amps (which isn't spec'd, but I would use in this configuration).

    Now, am I missing something basic here? Shouldn't that 18 gauge wire be larger (like 12-14 awg)?
    /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif /forums/images/graemlins/ears.gif
    TIA!
     
  2. Michael

    Michael 1/2 ton status

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    The switch is only switching the relay, which is very low current. The relay is switching the lights, which are higher current. That's why you would use a relay and not just a switch.
     
  3. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Your thinking about it wrong for the digram. He's using a positive trigger using the center pole of the swtich. The switch is only going to carry the the current needed for the trigger on the relay of about 400mA. You could run the switch on 22 gage.

    The reason he went with a Positive trigger was to make it easier to tap into the existing light circuit. He just "T's" ino the high beam circuit at the head light.
    In the top diagram he used a Negative trigger so he only had to run one wire to the switch and then a ground. On the top diagram I always run terminal 86 to 30.
    In the bottom circuit you don't have to go to 30 you just need a 12v source. If you mounting the relay under the hood then you just need to run the trigger wire into the cab to the center of the switch. a 12v constant or ign if you want them to shut down with the key, to the bottom and then a 12v trigger from the high beams to the top that you could catch right at the bukhead wiring block on the fire wall with a 3m T.
    He's got it right just got flaky with the wire he spected. 86 and 85 18-22 is fine (only about 500mA max in that path). Ffor 30 and the 87's I would use 12 since most of the lights your going to use should draw no more that 20amps and most of those relays are rated 30amp. .
     
  4. HarryH3

    HarryH3 1 ton status Author

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    I would add two more fuses to his circuit. Each power feed to the switch should be fused also. A 2 amp fuse in each feed circuit would be plenty. It's always better to blow a fuse than start a fire (or lose your headlights). /forums/images/graemlins/shocked.gif
     
  5. Skigirl

    Skigirl 1/2 ton status

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    Thanks guys! /forums/images/graemlins/thumb.gif

    Yea, Grim, I see what you're saying. Thanks for straightening that out. I am running 86 to 30 on my aux lights, but the driving and fogs I wanted set up to run with headlights and without (I know it's not legal, but especially with fogs, sometimes running headlights defeats the purpose). Versatility is my motto!

    And yea, I think I'll fuse that switch wire - can't have too many fuses!! /forums/images/graemlins/cool.gif
     
  6. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Nope you sure can't have enough fuses.
    What I plan to do is put a single fused post for the switches when I wire in the rest of my lights. That will fuse al lthe triggers for AUX lighting. That way I can run about 4-6 triggers off of one 7.5 and fuse. Then fuse each Relay individually. Then for my Hella Rally 1000's I'll hook it in for either Highs of on.
    Now on My wifes 79 I installed a AUX fuse box. I have one main line comming in off the battery feeding the thing with a 8 Gage feed. THen and individual fues fron there. It has 6 possisions and I wired 2 through a relay to work with IG and the other for straight power. I run the amps, Map lights, AUX Cig and head unit on it. Have a couple extra circuits that I have not used yet. It's mounted on the passenger side fire wall on the inside just below the blower box.
    I need to rewire the 75 and clean it up. Just been addig circuits as I need them but once I move the radio and CB overhead then I plan on a complete rewire. It's getting pretty messy after adding in the Bosch light, The rear lights, the rock lights and the mess that who ever put in with the trailer brakes and the stereo that was in it LOL. I still need to add in the Revers Halogons, Some aux interior lights off the cage (no overhead lights when you remove the top on a full vert /forums/images/graemlins/smile.gif, Map lights, Under hood light and cargo box light. I also plan to install a cig plug in the rear for my spot so I can plug it in back there if we need to work on a truck behind me. Looks like I need to add in about 10 circuits to make it work the way I wan't /forums/images/graemlins/grin.gif
     
  7. HarryH3

    HarryH3 1 ton status Author

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    Just keep in mind that feeding all of your Aux circuits from one fuse means that a short in any of them will disable all of them. /forums/images/graemlins/shocked.gif /forums/images/graemlins/wink.gif
     
  8. Skigirl

    Skigirl 1/2 ton status

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    Sweet idea on the trigger setup. And hadn't thought about lighting the cargo area - tho my dome light still works back there and it's unlikely I'll ever take that shell off.

    When I originally bought all the stuff I thought I needed for running the lights (about a year ago) I bought a 3 circuit fuse panel from Painless, 1 constant and 2 ign. But when it was shipped they left out some stuff and so shipped me another one and didn't want the one I had back. Well, once I actually looked at it, only thing missing was a couple of connectors and a 30 amp CB. Soooo....

    I'm setting up my aux lights and 2 power outlets off those fuse panels. Because my lights are hooked up to my rack, which is only on the shell, I'm routing those wires thru the shell, down the side, and I'm mounting the fuse panels and relays inside a work box that I'll attach to the side wall of the quarter panel. Then run the trigger wires about 4 feet to a switch bar I'm making from aluminum L channel and attaching to the lower front of my Tuffy console - it's only 1 1/2" wide, so won't get in the way of the shifter, but will be easy for me to reach.

    I'm wiring for 4 top front lights -2 inner on one line and outer on another; 1 rear light (stand alone overhead but also switched for reverse lights), 2 upper side lights, and 2 lights under the rig - which I'm wiring for but haven't installed. I have a couple old warn 410's that came with the truck and I hold out a slight hope that they would actually work. Otherwise I'll find something for under there. Of course, the guys will think they're rock lights, but I'll have em under there so I can see what the hell busted this time I drove to 7-11! /forums/images/graemlins/rotfl.gif
     
  9. Skigirl

    Skigirl 1/2 ton status

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    Hmmm, good point Harry.
     
  10. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    That's true but it's AUX stuff and the trigger circuts will not have near the worry of shorts as the stuff under the hood will. So if I smash a rock light and short it our the fuse for the relay (that would be mounted under the hood) would blow but not cause an issue with the trigger lines. So the likly hood of a short happening and taking out all the triggers is pretty small. It also mean I can run a single feed wire for the triggers and not 6-7 so a MUCH cleaner install.

    I also have a bunch of multi wire harness that has 6 wires inside it so all that will run too and from the swtich pannel that I plan to mount on the over head will be On 14 gage for the feed and two of the multi wire so it will be a much cleaner looking install since it will have to be zip tied to the roll cage to get there. Then I'll have the feed wires for the Stereo and CB. The speaker wires will go back down the the middle legs of the cage to where the speakers mount.

    For everything I want to mount up there I'm lookin a minimum of 16 wires but 12 of those will be in a pair of 6 wire harness that will be the triggers for the lighting since each circuit will only need to carry about 500mA each. . The main feeds for the Stereo and CB will carry the main trigger feed wire up and let me fuse at the switch pannel So just the 10 Gage main power will be needed for that. Fuse it down at the bottom for 20 amps and then 10 amps up at the CB and then at the stereo and 7.5 at the switch pannel.

    I need to meter out the draw on the ig trigger for the Stereo. It may only need 500mA as well and I can use one of the wires in the harness for it. That will let me have 3 main wires up and the two pairs of speaker wires back down to the rear.
     

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