Post by Mark on Mar 30, 2007 16:44:13 GMT -5
Wiring 101 and Quick Reference
You just got your Jeep and can’t wait to put all those high power fog and driving lights on it, just like you saw on that magazine cover. After a quick run to the store you’re back in your driveway with enough lights to land a jumbo-jet when your mini-van driving neighbor looks over and says, “Wow, nice lights. How much power are they going to use?” You already know the answer to that question. “600 watts!” you tell him proudly. His reply is, “How many amperes is that?” The blank look on your face says it all.
Ohm’s law will give you the answer you need. The part of it you need for the answer is this:
Watts divided by volts equal’s amps.
600 watts divided by 12 volts equals 50 amps
A quick reference for auxiliary light buyers:
A pair of 55 watt auxiliary lights draws about 9 amps.
A pair of 100 watt auxiliary lights draws about 17 amps.
A pair of 150 watt auxiliary lights draws about 25 amps.
The neighbor’s next question is “What size wire will you have to use?” Another blank look is your reply.
Wire comes in a wide assortment of sizes, gauges. The smaller the gauge number the larger the diameter the wire is and the more power, or amps, it can safely carry. For Example, a 4 gauge wire which is commonly used between the battery and starter can handle about 130 amps. A 14 gauge wire which you’ll find in many of the fog and driving light kits can handle about 15 amps. There are mathematical formulas to determine the exact gauge wire you need to carry X amount of amps over a specific length of wire but for most of us we’re dealing with a length of 10 feet or less. The quick reference chart below, which is conservative, is based on that:
Using too small a wire for the amps going through it will cause the wire to overheat. The longer the wire the greater the chance for it to overheat. The insulation on an overheated wire can soften. Repeated overheating can cause the insulation to become brittle and crack. In some cases the insulation can even melt and possibly catch fire. If in doubt go to the next size wire.
A relay contains a small electromagnet which is activated by a minimal amount of current. The electromagnet closes the contacts between 2 connections, allowing the larger amount of current to pass through. Relays are used to limit the length of the wires carrying power from the battery to the auxiliary lights. Most relays which come with auxiliary lights or bought individually at a store are rated at a maximum of 30 amps. Some relays have a single output connection and some have two outputs.
Below is an example of a fog light/driving light wiring diagram using a relay.
Always, always, always use fuses and make sure the fuse is the proper size, amp rating, for what it’s being used for. When installing the fuse holder put it as close to the power source as possible. The shorter the unfused wire the better. Read that safer. If you start blowing fuses for ‘no reason’ putting in a larger fuse is not the answer. There is a good chance there is a short-circuit and replacing the blown 15 amp fuse which came in your fog light kit with a 30 amp fuse is an invitation for disaster. Those 14 gauge wires are rated to carry only 15 amps. If those wires are shorted and you decide to try a 30 amp fuse those wires can overheat to the point the insulation catch’s fire. It’s the same for your stock fuse panel as well.
Upgrading to an H4 headlight system is a great to increase the amount of road or trail you’re able to see at night. You can buy just the headlight assemblies themselves or a complete kit which includes pretty much everything you need. It all depends on how much you want to spend and how handy you are with a wire cutter and crimper.
If you plan on using the legal, DOT standard wattage bulbs there really isn’t a need to upgrade your wiring harness because it’s not going to handle any extra amperage. But, if you’re planning on taking full advantage of the high power bulbs available you really should install a new wiring harness for your new headlight system. It’s easy to double the power requirement, amps, and those stock wires really aren’t up to the task. I should add there are cables advertised as ‘High Power” H4 adapters. You really don’t need them for DOT rated bulbs and they don’t do what you want with the high power bulbs. All those adapters consist of are a pair of sockets connected by short lengths of wires. One end connects to the existing headlight socket and the other end connects to the H4 bulb. All the power still goes through the stock wiring harness.
If you bought the complete kit just follow the instructions and all should be well. If you’re the make-it-yourselfer here is a simple wiring diagram:
It’s not hard to do but it can be tedious. Just take your time and think about what you’re doing.
With this set-up, whether you bought it or made it, it’s very easy to incorporate driving/fog lights which come on with your headlights; just like the new cars and trucks have. Remember, they need to utilize their own fuses and relays. Below is a simple diagram incorporating fog or driving lights:
If you do use those high power “Off Road Only” bulbs pay close attention to how your lights are aimed. Oncoming traffic doesn’t appreciate being blinded, especially when their lights are red and blue.
When you start adding more and more lights and/or stereo amplifiers you should take a look at your charging system. It might not be up to the task. If in doubt go talk to someone who actually knows what they’re talking about. If you’ve already put in a high power alternator look at the size of the power wire from the alternator to the battery or power distribution box. If you’re still using the stock wire you might want to replace it. Remember what can happen when you try to put too many amps through too small a wire.
Battery's which have both top and side posts can be a benefit when you start adding lights and amplifiers. The unused positive post makes those high-power hook-ups a lot easier.
Whenever you do wiring take your time and do it right. You’ve got too much time and money invested to risk having your Jeep go up in smoke.
You just got your Jeep and can’t wait to put all those high power fog and driving lights on it, just like you saw on that magazine cover. After a quick run to the store you’re back in your driveway with enough lights to land a jumbo-jet when your mini-van driving neighbor looks over and says, “Wow, nice lights. How much power are they going to use?” You already know the answer to that question. “600 watts!” you tell him proudly. His reply is, “How many amperes is that?” The blank look on your face says it all.
Ohm’s law will give you the answer you need. The part of it you need for the answer is this:
Watts divided by volts equal’s amps.
600 watts divided by 12 volts equals 50 amps
A quick reference for auxiliary light buyers:
A pair of 55 watt auxiliary lights draws about 9 amps.
A pair of 100 watt auxiliary lights draws about 17 amps.
A pair of 150 watt auxiliary lights draws about 25 amps.
The neighbor’s next question is “What size wire will you have to use?” Another blank look is your reply.
Wire comes in a wide assortment of sizes, gauges. The smaller the gauge number the larger the diameter the wire is and the more power, or amps, it can safely carry. For Example, a 4 gauge wire which is commonly used between the battery and starter can handle about 130 amps. A 14 gauge wire which you’ll find in many of the fog and driving light kits can handle about 15 amps. There are mathematical formulas to determine the exact gauge wire you need to carry X amount of amps over a specific length of wire but for most of us we’re dealing with a length of 10 feet or less. The quick reference chart below, which is conservative, is based on that:
Using too small a wire for the amps going through it will cause the wire to overheat. The longer the wire the greater the chance for it to overheat. The insulation on an overheated wire can soften. Repeated overheating can cause the insulation to become brittle and crack. In some cases the insulation can even melt and possibly catch fire. If in doubt go to the next size wire.
A relay contains a small electromagnet which is activated by a minimal amount of current. The electromagnet closes the contacts between 2 connections, allowing the larger amount of current to pass through. Relays are used to limit the length of the wires carrying power from the battery to the auxiliary lights. Most relays which come with auxiliary lights or bought individually at a store are rated at a maximum of 30 amps. Some relays have a single output connection and some have two outputs.
Below is an example of a fog light/driving light wiring diagram using a relay.
Always, always, always use fuses and make sure the fuse is the proper size, amp rating, for what it’s being used for. When installing the fuse holder put it as close to the power source as possible. The shorter the unfused wire the better. Read that safer. If you start blowing fuses for ‘no reason’ putting in a larger fuse is not the answer. There is a good chance there is a short-circuit and replacing the blown 15 amp fuse which came in your fog light kit with a 30 amp fuse is an invitation for disaster. Those 14 gauge wires are rated to carry only 15 amps. If those wires are shorted and you decide to try a 30 amp fuse those wires can overheat to the point the insulation catch’s fire. It’s the same for your stock fuse panel as well.
Upgrading to an H4 headlight system is a great to increase the amount of road or trail you’re able to see at night. You can buy just the headlight assemblies themselves or a complete kit which includes pretty much everything you need. It all depends on how much you want to spend and how handy you are with a wire cutter and crimper.
If you plan on using the legal, DOT standard wattage bulbs there really isn’t a need to upgrade your wiring harness because it’s not going to handle any extra amperage. But, if you’re planning on taking full advantage of the high power bulbs available you really should install a new wiring harness for your new headlight system. It’s easy to double the power requirement, amps, and those stock wires really aren’t up to the task. I should add there are cables advertised as ‘High Power” H4 adapters. You really don’t need them for DOT rated bulbs and they don’t do what you want with the high power bulbs. All those adapters consist of are a pair of sockets connected by short lengths of wires. One end connects to the existing headlight socket and the other end connects to the H4 bulb. All the power still goes through the stock wiring harness.
If you bought the complete kit just follow the instructions and all should be well. If you’re the make-it-yourselfer here is a simple wiring diagram:
It’s not hard to do but it can be tedious. Just take your time and think about what you’re doing.
With this set-up, whether you bought it or made it, it’s very easy to incorporate driving/fog lights which come on with your headlights; just like the new cars and trucks have. Remember, they need to utilize their own fuses and relays. Below is a simple diagram incorporating fog or driving lights:
If you do use those high power “Off Road Only” bulbs pay close attention to how your lights are aimed. Oncoming traffic doesn’t appreciate being blinded, especially when their lights are red and blue.
When you start adding more and more lights and/or stereo amplifiers you should take a look at your charging system. It might not be up to the task. If in doubt go talk to someone who actually knows what they’re talking about. If you’ve already put in a high power alternator look at the size of the power wire from the alternator to the battery or power distribution box. If you’re still using the stock wire you might want to replace it. Remember what can happen when you try to put too many amps through too small a wire.
Battery's which have both top and side posts can be a benefit when you start adding lights and amplifiers. The unused positive post makes those high-power hook-ups a lot easier.
Whenever you do wiring take your time and do it right. You’ve got too much time and money invested to risk having your Jeep go up in smoke.