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  #1  
Old 09-26-2005
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Wattage / fuse / fog light question

Got my hands on some fog lights that indicate they are 130 watt off-road fog lights.


What fuse size would I need to handle a pair of them, so that I'm not going to cause a blown fuse or worse??

How do I look this up? Is there a chart for it?
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  #2  
Old 09-26-2005
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you will need a 25A fuse (power= Current * Voltage)=(Power/Voltage= current) so you have 260Watts total/12V on the low side= 21.333Amps so go with a 25A Fuse

, as far as the wiring of it goes you want to do it with a relay, and a switch. Let me find a reference page for that for you.

dave
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Old 09-26-2005
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Well, I have all the wiring from my current fog lights, same size wiring, and switch.

25 is the way to go, eh?
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Old 09-26-2005
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Using the factory wiring with the 130 watt fog lamps will work for a short time, then it will damage the wiring if using the factory wiring is what you are talking about. A 25 amp fuse should be good to go, I would upgrade the wiring now so you dont have problems in the future.
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Old 09-27-2005
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No, not factory wiring. Its wiring I have for my current set of fogs on my safari bar. 55 watt pair, i think its 16 guage wire it's using.
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Old 09-27-2005
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I personally would upgrade just to be safe, but thats just me. I tend to overdo it when it comes to wiring.
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Old 09-27-2005
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What size? 12?
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Old 09-27-2005
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Yea I would go 12 or 14, at least 14 gauge. Your lights will perform better with the larger wiring as well.
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Old 09-27-2005
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Quote:
Originally Posted by aftermarket
No, not factory wiring. Its wiring I have for my current set of fogs on my safari bar. 55 watt pair, i think its 16 guage wire it's using.

First thing to check is the relay that came with your fogs. Was it a 5 pin SPST with two term. 87 or a 4 pin with one (this will determine whether you have a single lead or 2 leads of 16 gauge wire to the lights)? Also note the relay amp rating. Replace as needed. You may get by with two leads, but not for long.

If your running single lead 16 ga wire to both lights you will want to upgrade the wiring to at least 12 ga. You could leave what you have in place and just add another run of wire between the relay and lights.

On the fuse, I would run a 30 amp fuse. The 25 is being pushed close to its max by the load and will run hot and may pop.
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Old 09-27-2005
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Had no relay on the fog kit....using a seperate switch. These new ones I will use the previous fog switch, seperate from all the rest.
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Old 09-27-2005
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Quote:
Originally Posted by aftermarket
Had no relay on the fog kit....using a seperate switch. These new ones I will use the previous fog switch, seperate from all the rest.

In that case I would recommend putting in a complete new circuit. That much power through the switch will end in a melt down. You'll want to get a 40 amp 4 pin SPST relay and some 12 ga wire. You can use the switch and current wiring from there. Just connect the other end to term 85 on the new relay and hook term 86 to ground. the 16 ga wire is fine for this. Connect term 30 with 12 ga wire to 12V+ with a 30 amp fuse. Hook term 87 using 12 ga wire to the new lights and your done.
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Old 09-27-2005
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no less then 12 GA
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Old 09-27-2005
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The fuse is there to protect the wire, so you really choose the wire to meet your current draw, and then fuse the circuit so that the wire won't get too hot. In your case, you could use a #14 if you had to, but a #12 would really be appropriate. And then fuse it with a 25A as stated earlier. The #16 will start a fire worst case, create an open circuit and quit working at best. And you DO need to use a relay because of the current draw of this load. It's very hard to find a switch rated at 25A. Normally they're 6A-15A at best.

Don

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Old 09-27-2005
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Any suggestions on a type of switch?
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Old 09-27-2005
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normal rocker switch is fine. BTW are these KC's because there is a wiring kit with everything fuses relay switch and it isnt that expansive?
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  #16  
Old 09-27-2005
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No, it isn't.

These fogs will be a seperate line. Only connection to the truck is to the battery. Has it's own switch and wiring.

I still don't understand the value of a relay if i am not tying it into any of the truck's exisiting actual electrical system.
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Old 09-27-2005
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Quote:
Originally Posted by aftermarket
No, it isn't.

These fogs will be a seperate line. Only connection to the truck is to the battery. Has it's own switch and wiring.

I still don't understand the value of a relay if i am not tying it into any of the truck's exisiting actual electrical system.
Q: What's a relay and how do I know if I need one?

A: A relay is an electronic switch. When current flows through a relay as a result of a remote command, or of a switch being thrown in your vehicle, an associated security feature is automatically activated.

You need a relay any time the current demand of the accessory you're adding exceeds the current battery can supply. (Typical relay applications include door locks, trunk locks, dome light, etc., depending on the type of vehicle, the type of alarm, and the interconnect harnesses available.)

it keeps constant flow of engergy go ahead and dont use one and see the side affects of it.
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Old 09-27-2005
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SPDT Relay : (Single Pole Double Throw Relay) an electromagnetic switch, consist of a coil (terminals 85 & 86), 1 common terminal (30), 1 normally closed terminal (87a), and one normally open terminal (87).

When the coil of the relay is at rest (not energized), the common terminal (30) and the normally closed terminal (87a) have continuity. When the coil is energized, the common terminal (30) and the normally open terminal (87) have continuity.

The diagram below center shows the relay at rest, with the coil not energized. The diagram below right shows the relay with the coil energized. As you can see the coil is an electromagnet that causes the arm that is always connected to the common (30) to pivot when energized whereby contact is broken from the normally closed terminal (87a) and made with the normally open terminal (87).

When energizing the coil of a relay, polarity of the coil does not matter unless there is a diode across the coil. If a diode is not present, you may attach positive voltage to either terminal of the coil and negative voltage to the other, otherwise you must connect positive to the side of the coil that the cathode side (side with stripe) of the diode is connected and negative to side of the coil that the anode side of the diode is connected.

Diodes are most often used across the coil to provide a path for current when the current path to the relay is interrupted (i.e. switched off, coil no longer energized). This allows the coil field to collapse without the voltage spike that would otherwise be generated. The diode protects switch or relay contacts and other circuits that may be sensitive to voltage spikes. (JimR, contributor, install bay member)
Why do I want to use a relay and do I really need to? Anytime you want to switch a device which draws more current than is provided by an output of a switch or component you'll need to use a relay. The coil of an SPDT relay that we most commonly use draws very little current (less than 200 milliamps) and the amount of current that you can pass through a relay's common, normally closed, and normally open contacts will handle up to 30 or 40 amps. This allows you to switch devices such as headlights, parking lights, horns, etc., with low amperage outputs such as those found on keyless entry and alarm systems, and other components. In some cases you may need to switch multiple things at the same time using one output. A single output connected to multiple relays will allow you to open continuity and/or close continuity simultaneously on multiple wires.

There are far too many applications to list that require the use of a relay, but we do show many of the most popular applications in the pages that follow. If you are still unclear about what a relay does or if you should use one after you browse through the rest of this section, please post a question at the12volt's install bay. (We recommend Bosch or Potter & Brumfield relays for all of the SPDT relay applications shown on this site.)
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  #19  
Old 09-27-2005
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Quote:
Originally Posted by aftermarket
No, it isn't.

These fogs will be a seperate line. Only connection to the truck is to the battery. Has it's own switch and wiring.

I still don't understand the value of a relay if i am not tying it into any of the truck's exisiting actual electrical system.

A relay allows a low current control (Switch) to control and switch a high current device (Lights). It works the same way a transistor does...low power input to control a higher output. Think of it like a power amp for your stereo. You add an Amp to boost the power to the speakers that your stereo cant provide and power the amp from the battery and not the radio.

The switch you have now will not take the current demand of the lights...it will melt...as well as the 16 ga wire.

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  #20  
Old 09-27-2005
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So to find a relay, where would I look? AutoZone?

And what size or rating?

We have those types of automotive shops up here, I guess that would be the best place to start?
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Old 09-27-2005
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radio shack sells good one's a 30-40 amp should be fine
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  #22  
Old 09-27-2005
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So lets say, hypothetically, that I had some Hella 55W aux. lights, and theres a bulb I want to use thats only available in 70W. (odd, yes, I know.) How unsafe would it be to use 70W bulbs with the stock harness?
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  #23  
Old 09-27-2005
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It would be ok for awile, most of the aftermarket headlamps are higher wattage rating then stock and dont cause that much damage. Any more then 75 watts and would get questionable, it would hurt to run some new circuits to be safe though Brian.
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  #24  
Old 09-28-2005
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Def. wouldn't be going for more than 70w.. and I'm only looking at that because I can't find the bulb I want in 55w.
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  #25  
Old 09-28-2005
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Ok, an Update......


Went on the advice to visit Radio Shack.....picked up a relay (30 amp size)....


Now....where does it get installed? Close to the battery? Close to the switch in the cab?

And when it says "12v in" #87, is that coming from the battery, and #30/51 "12v out" goes to the lights them selves?
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