FOG LIGHTS!

jlh0799 · April 29, 2003

I had a front end replacement bumber put on my truck and so the factory fog lights were disconnected. I bought new fog lights (6" 130Watt Pro Comp Lights). Now to my Question....can I use the existing wiring harness that went to my old fog lights to hook up the new pro comp lights? Can the wires handle the load produced with the new lights or do I need to get a nother wiring harness? Thanks in advance!!

BadBowtie · April 30, 2003

I think that the larger new lights will draw too much current. I would just wire them into a new circut. The factory lights that I have seen are not very bright, and probably are not wired using a very heavy gauge wire. I'd play it safe and use heavier wire.

jpendlum · April 30, 2003

I switch out my factory fogs with 55 watt fog lights and hooked them up to the factory wiring. I haven't had any problems so far (over 8 months) and I burn my fogs all the time.

BadBowtie · April 30, 2003

However, you are only using two 55W bulbs, he wants to use 2 130W bulbs. Your lights would pull around 8 amps, while his would be drawing around 18amps (does this sound right?). I would definately not want to attempt to run close to 20 amps through the factory 16ga. wiring. JMO

-John

jlh0799 · May 1, 2003

What gauge wire would one suggest for the type of lights I am using?

BadBowtie · May 1, 2003

I had some 10ga. stranded that I had left from a commercial lighting project that I was doing, so I wired my lights using that. You could probably get away with 12ga stranded, however. It is cheaper and a little easier to work with.

-John

jpendlum · May 2, 2003

I agree with you Badbowtie. I thought he was just using 55 watts per. If I were to go any higher I would definitely wire them alone.

jlh0799 · May 4, 2003

Thanks for the advice. I talked to the dealer and they suggested to use 14 gauge wire for 130 watt bulbs. I am in the process of installing the lights this weekend. I have the wire put in except for inside the cab. Not quite sure how to remove the Bezel though. I think it is just pull out/push in? From what I have heard. I am wanting to put the switch next to the Switch for turning the Passenger Side Airbag off and on. I will try to post som pics when I am done.

BadBowtie · May 4, 2003

14 is still awfully small. Even for the 10amp loads of Minilighbars and stop lights (reverse lights) used on out trucks and other guys plow rigs, we use at least 12ga. The idea is to provide the wire the path with least resistence, therfore there is a little current draw as possible. When the pump motor pulls close to 200amps, you can easiy overwhelm a stock charging system with too many power-robbing electrical accesories running, or poor connections.

Lets assume that your truck runs at 14.0 volts when the engine is running: [(130watts x 2lamps) / 14.0volts]= 18.57amps. I think that would constitue the use of 12 gauge. Like I said though, If you have access to it, 10 ga. would be ideal, keep in mind, that is nearly 4x the draw of a stock headlight.

-John

bummed-n-Md · May 7, 2003

If you are pulling anything greater than 15 amps, you must go to 12 ga. and was stated, 10 would be better.

when you install the fogs, you will probably need to use a minimum of a 20 amp fuze (unless you can find an 18.57 fuze somewhere which by the way would probably blow everytime you turned on the lights due to 'surge' currents). By using a 20 amp fuze, the wiring and all connectors must also be capable of supporting 20 amps.

If you run 14ga, you run the real risk of overheating the wire, melting the insulation and either shorting it out or possibly causing a fire. (the wire will fail before the fuze does.)

With electrical systems, the fuze (or circuit breaker) should be never be valued higher than any compontent in the circuit. It must be rated the same or less then the components it is protecting, to include the wiring and connectors.

BadBowtie · May 7, 2003

More good advice that I forgot to include.

bummed-n-Md · May 7, 2003

I talked to the dealer and they suggested to use 14 gauge wire for 130 watt bulbs.

The only reason I could see the dealer telling you to use 14 is that he is expecting you to run separate wires to each light. This is still 9.5 amps per wire and 'borderline'.

the safety issue is:

You will still need a 20 amp fuze just to turn them on (unless you wire in each light on its own switch and circuit and use a 10 amp fuze for each circuit). However, by using a 20 amp fuse, if there is a problem with one wire, that wire (or the remaining one) is still capable of drawing the whole 20 amps, so you still need 12 or better.

My previous advice still holds, the fuze is always the 'smallest' rated item in the circuit.

rtbrick · May 21, 2003

Can the stock fog light switch be re-used when installing those aftermarket foglights? I am looking at the PIAA air dam and a set of PIAA 520s. The 520s are rated at 55w.

buffy · May 21, 2003

Alright Aggie-Man,

Here's the beef. I recommend using a relay to control the power going to your 130W lights. They're pretty straightforward. You have a ground wire, a wire directly to the battery, a wire to your control switch, and a wire to the lights. A relay is pretty straightforward. It uses a low current to control a large current. The switch you use is one of those on/off, toggle switches. An auto parts store will have a big selection of fancy looking switches. You typically power the switch with an ignition hot circuit.

Here's a great little product that allows you to tap into the fuse box on the left side of your dash without cutting any wires:

http://www.wranglernw.com/commerce/ItemDet...temNo=30%2D545A

All you have to do is look at your owner's manual to figure out the ignition hot circuits (like AC or radio)

You can pick up an auto relay at any auto parts store. 30 amp should do. Same with the switches and wire. I agree on the gauge thing. I would get at least 12 gauge. No reason to push it with 14 gauge.

I'm ramblin'....Anyway, when you have that low current flowing through your switch (ON), it's setup to generate an electric field, within the relay, that closes the circuit (aka connects the wire) for the big current. That way, you don't have to send 30amps through a switch to control your on/off. Kinda cool huh

As for your idea about using the factory fog light switch.....I wanted to do the same thing you're trying to do with the factory fog light switch. The problem I discovered is the factory fog lamp switch is a momentary switch. It doesn't work with your generic relay. It works by sending an 'on' pulse to a relay. Basically, power is only going through the switch when its pressed. To make this work, I think you need another kind of relay. I know the factory foglamps run off a relay, but I'm not quite sure how that's wired to work. It's possible that the factory relay is large enough and you could wire into that. I couldn't figure it out, but that doesn't mean a qualified auto-electrician couldn't give you some advice.

Regardless, your factory fog lamp wires aren't big enough for your 130 W lights. A relay is the safest way to control big currents from big lights.

One more thing, definitely put a 20 or 30amp fuse on the wire from the battery to the relay.

Word.................