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Discussion Starter · #1 ·
i got two pairs of 55w fog lights from harbor freight. do you guys think its ok to wire all four to one wire going to a switch, or should i wire all four seperatley going to the switch, or will i have to get a relay?
 

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For all practical purposes that's 20A at 12V.... you need to make sure the switch is rated for that, MINIMUM of 12 gauge wire (according to 'Uglys'). But if you want a long-term, safe, reliable setup, that much current will wear out the switch contacts, and eventually the switch will fail and then you will let the magic smoke out.... USE A RELAY!
 

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itsmeagain5789 said:
i got two pairs of 55w fog lights
the inrush current on 220W of incandescent lights will make quick work of killing the contacts in even a 20A rated switch. for reliability, i would do this with two relays, one for each pair of lights. at minimum, one big ass (at least 30A) relay for all four.

i would not even consider hanging four lights off of the switch. you are going to drop a lot of voltage going from the battery back to the switch and then up to the lights. the result is going to be dim (yellow) lights. there is a reason that hefty relays are included with good light kits... and that's just for a pair of lights.

in summary: have the switch control a pair of relays, one relay per pair of lights, and keep the wiring carrying power to the lights as short as possible. this setup will provide the best reliability and the best light output.

jim aka the wrooster
 

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i would agree that relays are the way to go. i have bed lights and front lights on relays. i have learned my lesson years ago when i overheated the switch and almost burnt my truck up. easy to wire and not real expensive either.
 

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No question = relay it.
 

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Discussion Starter · #7 ·
yea, im definatley gonna relay it, and probably add a 25 or 30 amp fuse in front just to be safe. does anyone know if the toyota fog light (old fashioned one with one with little orange light on it) switch can handle that many amps?
 

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itsmeagain5789 said:
yea, im definatley gonna relay it, and probably add a 25 or 30 amp fuse in front just to be safe. does anyone know if the toyota fog light (old fashioned one with one with little orange light on it) switch can handle that many amps?
it won't matter.

powering either one or two relays will draw at most 1A through the switch.

in case you are not understanding this: in the setup you will be using the switch simply powers a small electromagnet in each of the relays. the electromagnet draws two beefy contacts together -- and those beefy contacts handle the high current going to the lights. whether the lights draw 10 amps or 10 thousand amps, it doesn't matter to the switch. the switch only carries a tiny current to power the electromagnet (which is a small coil of wire wrapped around a ferrous core).

jim aka the wrooster
 

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Discussion Starter · #10 ·
Update:

i've decided to hold off on one of the pair of fog lights, so that just leaves me with 110 watts. i guess, 10 amps, right? i ran this same setup on my 4runner with no problem, but i dont want to risk something happening to my new taco, do you guys think i should go for the relay now or just hook it up to the switch?
 

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Again... no question = relay it.

1, 2 or 12 lights, it doesn't matter. Whenever you run high wattage lights you should ALWAYS relay it.
 

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itsmeagain5789 said:
i've decided to hold off on one of the pair of fog lights, so that just leaves me with 110 watts. i guess, 10 amps, right? i ran this same setup on my 4runner with no problem, but i dont want to risk something happening to my new taco, do you guys think i should go for the relay now or just hook it up to the switch?
let's see...

option A: wire the lights to the switch --> lights are dimmer, wiring gets hotter, switch contacts wear out quickly, and you have to rewire the whole setup to add another pair of lights.

option B: wire the lights through a relay --> lights are brighter, no overheated wiring, switch contacts last forever, and adding another set of lights in the future is dead-nuts simple.

what to do, what to do, what to do???


bummer that the relay costs a whole US$7.50 though.
that's like 2 Starbucks lattes or thereabouts.

jim aka the wrooster
 

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Discussion Starter · #14 ·
No go on relay. HELP!

I just plugged in my relay, and no go. it is the radio shack 30a relay. i've looked at just about every diagram on the internet and tried everything. heres what i got
#86 goes to switch. other end of switch is grounded
#87 goes to lights. other end of lights are grounded
#30 goes to positive side of battery. battery is grounded on other side :p
#85 is ground.
i tried for about half an hour, looked on the net for some other diagrams, and still nothing, i may have heard a click a few times in the relay, but no lights, and the lights do work, ive tested them.
 

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itsmeagain5789 said:
I just plugged in my relay, and no go. it is the radio shack 30a relay. i've looked at just about every diagram on the internet and tried everything. heres what i got
#86 goes to switch. other end of switch is grounded
#87 goes to lights. other end of lights are grounded
#30 goes to positive side of battery. battery is grounded on other side :p
#85 is ground.
i tried for about half an hour, looked on the net for some other diagrams, and still nothing, i may have heard a click a few times in the relay, but no lights, and the lights do work, ive tested them.
Try this
http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/relay.htm

Aaron
 

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itsmeagain5789 said:
I just plugged in my relay, and no go. it is the radio shack 30a relay. i've looked at just about every diagram on the internet and tried everything. heres what i got
#86 goes to switch. other end of switch is grounded
#87 goes to lights. other end of lights are grounded
#30 goes to positive side of battery. battery is grounded on other side :p
#85 is ground.
i tried for about half an hour, looked on the net for some other diagrams, and still nothing, i may have heard a click a few times in the relay, but no lights, and the lights do work, ive tested them.
from above, your connections are incorrect. there is no power to the relay coil as you have it wired.

forget about the connections to the lights for a moment. disconnect them entirely.

wire this up:
#86 goes to the switch. other side of the switch goes to the battery POSITIVE.
#85 goes to ground.

test this now. flip the switch, the relay should click. flip the switch back, you should hear the relay release. if you do not hear the click at this stage, stop. do not proceed if there is no click when you turn on the switch -- nothing you do after this is going to work nor is the problem miraculously going to get fixed.

the next step is to connect up the lights.
#30 goes to positive side of battery via a 20 to 30A fuse.
#87 goes to lights. other side of lights are grounded.

flip the switch. bingo, now the lights work.

jim aka the wrooster

EDIT:
just so we are on the same page:

the wires to #30 and #87 should be as short as possible and as heavy as possible -- these are the wires carrying the high current from the battery to the lights. 12AWG is a good place to start, and 10AWG is sufficient for all but the highest power lights.

the wires to #85 and #85 can be as long as you want and can be much thinner -- these wires are carrying very little current, just enough to power the little coil in the relay. 20AWG is fine.

the net sum of the above is that the relay should physically be located pretty much on a direct line between the battery and the lights. your goal is to minimize the length of the high current carrying (heavy gauge) wire, and that means positioning the relay somewhere along the shortest route between the battery and the lights. it doesn't matter how far the on/off switch is away from the relay -- it could be 25 feet away and even that will have ZERO effect on the lights. so, keep the high current (heavy gauge) wires short and put the switch anywhere you want. otherwise, you are defeating the purpose of the relay. for lights mounted on the front bumper, for example, in no case should the relay be mounted under the dash. the relay for my ARB-mounted IPF 968's is right next to the battery, and the heavy wiring runs direct from the battery to the relay and over to the lights. no heavy gauge wires run into the cab, just the thin stuff that powers the little coil in the relay.
 

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Discussion Starter · #17 ·
figured it out guys, thanks for the help. i wasnt running power to the switch, i didn't think i needed too, but all is good. thanks again.
 
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