I won't lie, I dont know how a relay works. Wiring a light bar, need help.

I know how I'm going to run the wires. Just don;t know what to use.

I had planned to run a single 12ga. positive to the light bar. I was told that I should use a relay, I never worked with a relay before. If I run a fuse in-line do I still need a relay?

How would you wire one into a light bar with 5 lights?

Thanks guys!

In simple, a relay is a switch you use for a high load in between the source and the load, and you can then control it remotely with a smaller switch. This allows you to run your power line more directly (reducing conductor losses) as well as using pretty much any switch you like - since the switch need not be rated for the load (just the relay. The relay sinks something like .01A to "make" a circuit - and you'd have to go rather small to find a switch that won't handle that.)

A relay does not replace a fuse - you should still have a fuse AND a relay in circuit. A relay just allows you to run a shorter lead to the accessory you're controlling.

In order to give you useful information, I'd need to know more - but I'm inclined to think that you may need two relays (a lot depends upon the load...) to control all the lights. A switch can "trip" several relays at once - it's all in the wiring.

Tell me more...

They are Halogen driving lights, came with a 15amp fuse and 12v switches. I plan to throw out all the electrical stuff that came with the lights and use quality stuff.

What else do you need to know?

So let me make sure im uderstanding this. I can run a fused accessory (doesn't need to be a full 12v) with a switch in-line before going to the designated prong on the relay.

Then I take a full 12v from the battery with a fuse in-line to its designated prong on the relay.

Then from the remaining pring I go directly to the lights.

I assume the relay has a ground prong as well?
To control say my two outers and my 3 inners on the bar I would just use two differnt setups as described above?
What amp relays should I be using to have 2 switches?

This stuff isn't as hard as I had thought

Thanks 5-90!

Your standard DIN relay (the Bosch/Hella ones that are used all over the XJ - they are about a cubic inch in size) has five prongs. The are numbered 30, 85, 86, 87, and 87a.

Pin 30 is used for the power supply to the accessory. Typically, the fuse goes between the relay and the source (so the lead to pin 30 has a fuse inline.)

Pins 85 and 86 are for the coil (the part that pulls the contacts together) - and they are not poarised. One will go to a ground, the other to a switched power source (my convention is to ground pin 85, and put the switched power to pin 86.)

Pin 87 is a "Normally Open" contact that is closed when the relay is powered - that's the one you're going to use.

Pin 87a is a "Normally Closed" contact that is opened when the relay is powered - which allows you to manually turn something OFF when it's normally on. Pin 87a isn't used a lot.

You can also find DIN relays with two pin 87 and no pin 87a - these are "DPST" relays, and are usually used to power two circuits (like two lights, when you want to run individual leads to them.)

Relays (and switches) may be used for anything below the ratings given - you don't need to run a full 12VDC (nominal) through a relay. You can use them to switch microvolt signals, but it's kind of pointless (microvolt signals are typically also microampere signals.) However, if you've got something that draws three volts at a dozen amps, a DIN relay will work for you there as well. You can always work below a rating, never work above a rating!

If you get true DIN relays (like from Bosch - I use theirs exclusively,) you'll have a "reminder" of the internal arrangement and terminal functions mounted in one side of the relay cover.

Mainly, what I need to know is how many lights of what wattage you're running, and if you want to be able to turn some of them on independently, or all at once (like, say, turn on the end two or middle three, or are you powering all five at once? It makes a difference in wiring.

Again:
Pin 30 - Fused lead from source voltage (usually the battery.)
Pin 85 - Ground
Pin 86 - Switched Low-Current power (from your toggle switch)
Pin 87 - To Accessory
Pin 87a - No connection.

^Ok I uderstand all that, so my pin 86 would bo to a toggle switch then to the lights right?

I want to run the two outers on one switch and the 3 inners on another switch. Again, thanks for your help.

Hope this this isn't confusing you like did me.

Plays For Jeeps said:

^Ok I uderstand all that, so my pin 86 would bo to a toggle switch then to the lights right?

I want to run the two outers on one switch and the 3 inners on another switch. Again, thanks for your help.

Click to expand...

All I need now are what wattage of bulbs you plan to run where...

Ok, I can get that to you when I get home and look at the actual instructions for the lights. I have always just ran a fused 12v to the switch and then to whatever I was going to power. I didn't realize I was so far from the proper way of doing things.

Plays For Jeeps said:

Ok, I can get that to you when I get home and look at the actual instructions for the lights. I have always just ran a fused 12v to the switch and then to whatever I was going to power. I didn't realize I was so far from the proper way of doing things.

Click to expand...

Half of the time, the fuse you get with the kit is oversized for the application (and the rest of the time, it's a glass tube anyhow, so I tend to want to use ATO/ATC fuses anyhow. They're used everywhere else - that's those coloured plastic "blade" fuses.)

The fuse is sized to the demands of the accessory. I'll typically figure the current needed at a nominal 12VDC (it's actually a touch less, since operating voltage is more like 13.5-14VDC) and go with the next higher fuse than the calculated rating. That gives me a safe margin for startup surges and things like that.

When you've got the information, let me know, and we'll come up with a plan for your wiring. Deal?

Check out these 2 links for more info.
.
http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/relay.htm
.
http://www.classictruckshop.com/clubs/earlyburbs/projects/bosch/foglites.htm