so I got some rock lights and ive been reading thru some posts where relays are mentioned. I wanted to know what is the purpose of the realy and how to wire. Also, where whould I pick up some of the relays.
Ok go buy an electronics book. Somthing like electronics: the easy way. I have that one.
I relay is a high amperage switch. Most of those little switchs on your dash can run, lets say, 20 amps(amp: a measure of how much electricity is flowing) or so through them untill they melt down(like on fire bad). Relays can hold hundreds of amps before they melt down. Think about your starter. you dont have 250 amps running through your ignition cylinder do ya? no, you have small wires which turn on the large relay, which allows electricity to flow to the starter.
Lets talk about those rock lights now. how many watts are they? The way you find how many amps those light are going to need to run is very simple. to find amps you use watts / voltage = amperage. So most lights are 55 watts, your car runs around 14.6 volts, so one 55 watt lamp runs on 55 / 14.6 = 3.78 amps.
My switchs are rated at 30 amps(more expensive quality units), so I usally run 2 lights per switch. Granted, I only HAVE two extra lights. On the limo, I will have a bunch of lights, so all of those will be hooked up to relays. They will also be at 120 watts each, so they dram more power than the little 55watters.
You can purchase relays at any parts store, but they mark them up alot. Try online electrical places for good prices. Also try 12voltguy.com. His stuff is sweet! (insert some you sould advertise in my limo comment here 12voltguy).
a relay is an electromagnetic switch. Inside that little plastic box is a small electromagnet and a piece of spring steel. when power is applied it pulls the spring steel to it and completes the circuit.
A relay allows you to switch a high power circuit using very little power. The reason you have relays in a vehicle is so you do not have to run big ass wires to big ass switches all trying to find a way to cram under your dash.
wiring a relay is easy.
(stolen from 12voltguy.com)
or if you want to run multiple switches to turn on one light (like a dome light you want all doors to turn on or a reverse light you want switched by the reverse switch AND a dash switch) you can make it "ground switched"
you run 30 to the battery, 87 to the lights, a jumper wire from 30 to 86 and you put the switches off 85 now any time that 85 is grounded the relay trips and the lights come on.
This is also handy if you are running electric cooling fans and want a "manual override" switch in case the thermostatic switch dies for some reason
I learned to only buy the Bosche ones for high amp. stuff like lights and fans, etc. My KCs would burn up the cheap-o relays when running a pair per relay. Most of the cheap ones are rated at 30-35 amps but they won't even handle that. The good Bosche ones are rated for 40 amps and actually handle it.
I just want to say, if you need a BUNCH of relays(like 30 or more in the limo) goto a junkyard. Look for the newest(model year wise) cars and trucks. Pop the fuse blocks, pick away at the correct size ones! They are almost allways bosch, and dont cost you a think vs. about 35 bucks apeice for the same ones.
thanks for the for everyones reply. What I needed was just a high level over view. I totally forgot about the starter relay and the way it works, after reading over this I totally get it now.
I got some 30 amp toggles and 30 amp relays for at most eight lights which are 55w. Even if I were to run 4 lights per toggle and relay, that should only be 20 amp at most.
Don't forget, a relay does NOT get rid of the safely of a fuse. At LEAST put a fuse on the high current side of the system, and possibly put a small fuse on the low current side (switches get crushed in flops, start arcing, create electrical havoc)
Why use a relay in the first place?
1) The switch will fail after a while, even when rated for 30 amps, unless you use a 120 volt household light switch.
2) Saves money on wiring, you only need to run heavy 12 gauge wire to the lights and not back to the switch.
3) Brighter lights, small gauge wire will have enough voltage drop to dim the lights.
Where to get them? I like the weather proof ones off cars at pickNpull.
P.S. don't assume all the black wires are hot on your rock lights, I bought 2 sets and one set was wired backwards :mad3: The black was grounded to the frame of the light, took a few fuses to figured that out.
You can buy ready made realy's from many people hella and the like.
the next thing to do is work out if your rig is Positive ground or a negative ground as if you wire this up nothing will work and you will spend hours trying to work out WTF is wrong with it!
Heck with all those relays! Not to step on your thread but I have found in the past that 55 watt rock lights have always been an issue pulling too many amps.
We have LED rock lights that don't need relays. Leave them on all night and your rig will start in the morning. http://www.roundeyes.com/LED_Lighting-LED_Rock_Light_Kit.html
12volt guy has some nice stuff and is quick on shipping.
I see the 3 watt led's have come way down in price. anything new comming soon?
How come your 1 watt leds don't have a reflector to help focus the beam, or do you offer an option to control the light beam. I have a 1 watt led heap lamp and it's way bright.
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Pirate 4x4
18.7M posts
366.4K members
Since 2000
A forum community dedicated to custom off-road vehicle owners and enthusiasts. Come join the discussion about trail reports, builds, performance, modifications, classifieds, troubleshooting, fabrication, drivetrain, and more!