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  #1  
Old October 28th, 2004, 22:51
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ghettocruiser ghettocruiser is offline
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Lightbulb Lights lights and more lights...

Ok..I have a simple question. I just aquired 4 6" round chrome off-road lights from work...almost free of cost. So of course Im going to use them. They are 100W a piece. I already made a light bar...so they are on. Here is my question. The instructions show that its ok to use their 25A switch, and basically power the lights from the battery, through the switch, to the lights. No mention of a relay. Now all the other lighting systems and other accesories I have hooked up in the past have used relays...even stuff that didnt require a relay. Mostly because I was using a small switch. But with the switch they supply, with its high amperage, is it ok to run with no relay??? I have searched and found some posts saying relay...some saying not. So whats the best way?

I think I should say that these are more for looks than anything else. I will rarely be running them all on at once, and I plan to have two lights to a switch..i.e. two switches. But if Im ever wheeling at night, I want them to work proper. Let me know what you all think. Thanks in advance....

Justin
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Old October 28th, 2004, 23:06
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Re: Lights lights and more lights...

Each light will draw 8-1/3 amperes while ON, and a little more when they light up. You could safely run three, four would cook the switch. Even odd if starting three will cook the switch - that's 25 amperes.

The way I'd do the job would be to wire to a pair of relays under the hood near the battery, and a brace of 10A fuzes to be safe (10A will be a comfortable rating for that load - run one for each light.) The switch will have no trouble at all triggering the relays, and you shorten the path for the hard power to take and take the load off the switch and put it onto something that designed to handle the load, switch it effectively, and is easier to replace. That will also allow you to select whatever switch you care to use for appearance sake - toggle, paddle, button, or whatever.

5-90
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Old October 29th, 2004, 00:06
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Re: Lights lights and more lights...

You really should go with the relay. I have seen many switches that were rated for a specific amount of amps, actually handle the amount of amps that they should, but get extremely hot after prolonged use, which caused them to melt the plastic dashboard that they were mounted to and then make a big mess.
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Old October 29th, 2004, 07:29
dmillion dmillion is offline
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Re: Lights lights and more lights...

Watts = volts x amps. So, 400 watts = 12 volts x 33.3 amps. That means your 25 amp switch is NOT enough!

Do a relay. Like the others said, that would be best. If you really don't want to do a relay then you must use a switch rated to AT LEAST 35 amps!
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Old October 29th, 2004, 08:41
kmagnuss_2000 kmagnuss_2000 is offline
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Re: Lights lights and more lights...

I had a electrical fire in my 94 yj cause I didn't use a relay. Good thing I had the fire extinguisher. Now I use relays.

-Keith
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  #6  
Old October 29th, 2004, 09:48
Jay3XJ+ Jay3XJ+ is offline
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Re: Lights lights and more lights...

Relays could end up being cheaper as well. Switches that can handle high DC currents can start to get expensive in a hurry.
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Old October 29th, 2004, 12:59
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Re: Lights lights and more lights...

Hey thanks for all the input. I by no means thought one switch would do it...I had planned for two. One for the outisde two, and one for the inside two. But...I think I am going to do relays. The switches that are rated for high amperage are pretty big and bulky, and Im running out of places to drill holes for switches.
I think I am going to go with relays. What kind of relays will work? Will regular old "Pilot" style relays handle that much? Or do I need to get a high amp relay from say hella or something?
I actually had another question about relays... Where does everyone mount them? I have three under the hood now...one by the batt, one on the firewall, and one on the drivers side fender. I would like to centrally locate all my relays...posibly use the same type for each circuit. Does anyone have any trick ways of mounting relays? Maybe a relay "box" sort of like the power center thats there now? I saw a buick skylark that had a nice rack for the relays on the firewall... Give me some ideas. Thanks again for your help. Very useful in making up my mind...

Justin
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Old October 29th, 2004, 13:14
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Re: Lights lights and more lights...

I use the regular Bosch/Hella relays - they can be had pretty much anywhere, and you should be able to walk in and buy Bosch brand for less than $10 (or find them on mailorder for even less - I think Parts Express carries them - www.partsexpress.com) I wouldn't go cheap here - what you save the first time you'll use up in replacements.

There are two types of relay to use here - SPDT and DPST. SPDT stands for Single Pole Double Throw, and is a switch for a single circuit to choose from two options (kinda like an A/B switch.) DPST is Double Pole Single Throw and switches two loads on and off at the same time. Both are rated for a 30 amp load, and are about an inch on a side (not including terminals.) Sockets and mounting blocks are readily available.

For mounting location, find a comvneient spot under the hood, preferably near the battery or in between the battery and most of the loads (physically.) Part of the reason for using a relay is to lessen the amount of wire that has to carry high current, making for a reduced risk of electrical fire (get enough mods, and you'll appreciate it,) less wear on the switch (due to high-current switching) and less line resistance (meaning more power sirectly to the light.) It also offers the advantage of a smaller user switch and you will probably never have to replace that switch, either!

Since the relay is rated for 30A, I'd run a pair to control all four lights. This not only eases the job of the relay (think component longevity here) but also gives you the option of switching the lights in pairs later if you decide to. Given the cost of relays, there's no real reason to not split loads for upgradability, safety, or service reasons. Another relay is WAY cheaper than a replacement XJ!

5-90
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  #9  
Old October 29th, 2004, 16:30
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Re: Lights lights and more lights...

5-90...Thanks a lot. That was pretty much exactly the info I was looking for. So I should use a DPST relay for one pair of lights? Im definetly going to get some good relays and try to make a nice power distribution block near the battery. Thanks for the info again... any more help is still welcomed!!

Justin
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Old October 29th, 2004, 16:46
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Big Red Big Red is offline
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Re: Lights lights and more lights...

What's up 5-90? I remember you from the Hollister Run early this year. I had the silver 2 door that showed up late after you guys were extracting Letterman's rig from the rivine. Pretty impressive wiring tech there man.
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  #11  
Old October 29th, 2004, 16:55
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Re: Lights lights and more lights...

Yah - I'd do it that way (in fact, I usually do!) Check out Parts Express - I seem to remember them having Bosch relays for good prices. Make sure to buy Bosch or Hella branded relays (Hella units are Bosch anyhow,) so you've got something good for starts.

I go to marine supply houses for most of my supplemental electrical stuff - like West Marine or something like that - since most of what they have is designed for being in the wet and nasty places anyhow. That, and the prices are usually pretty good (and worth it if it costs more than something somewhere else!)

Big_Red - I'm sure we've met somewhere, but I hate to tell you that I've not been to HH. Maybe at Farmer Matt's or that place down by Bascom & Union? I do have a boatload of electrical mods, and while the wiring isn't as clean as I'd like, I'm still pretty happy with it all... You are thinking of a tall guy with a dirty white 2-door Laredo - lots of stickers in the back window?

5-90
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