Do I Need a Relay

Modified and aftermarket systems, lights, wiring, etc.

Moderator: F9K9

User avatar
groceryman
Enthusiast
Enthusiast
Posts: 30
Joined: Sun Oct 15, 2006 2:21 am
Location: Reidsville N.C.

Do I Need a Relay

Post by groceryman »

:( I need help with the lights on my safari bar i had two 55 watt pro comps lights on it wired to the fuse box and rocker switch worked fine. Now i have added one more pro comp 55 watt and when i cut them on now the amp gauge drops do i need to install a relay if so what type never installed a relay before Thanks for any help
User avatar
HenryJ
Admin K Elite
Admin K Elite
Posts: 12705
Joined: Tue Oct 01, 2002 9:14 pm
Location: Ontario, Oregon
Contact:

Post by HenryJ »

The idea of using a relay is that the switch to activate the lights is not capable of carrying the load, or would create undue resistance in the circuit.

You do need a relay to provide the power needed for your lights. It is also a nice safety feature. The relay contains a coil and when overheated it tends to fail. This saves burning down the wiring.

12Volt.com is an excellent resource. Start with the basics: Relays
12volt.com wrote:Why do I want to use a relay and do I really need to? Anytime you want to switch a device which draws more current than is provided by an output of a switch or component you'll need to use a relay. The coil of an SPDT relay that we most commonly use draws very little current (less than 200 milliamps) and the amount of current that you can pass through a relay's common, normally closed, and normally open contacts will handle up to 30 or 40 amps. This allows you to switch devices such as headlights, parking lights, horns, etc., with low amperage outputs such as those found on keyless entry and alarm systems, and other components. In some cases you may need to switch multiple things at the same time using one output. A single output connected to multiple relays will allow you to open continuity and/or close continuity simultaneously on multiple wires.
I usually go to my quadbeam page and use the diagram I made for wiring a relay:

Image

relay "activate +"(#85) , relay feed (Normally Open #30) , relay supply (#87) and to relay "activate - " (#86).It is not a bad idea to use a switch to ground the relay for activation. That way you don't have a hot wire passing the firewall and only one wire to the switch , as the other side of the switch can be grounded.
Last edited by HenryJ on Sat Sep 29, 2007 2:36 pm, edited 1 time in total.

"Speed doesn't kill, suddenly becoming stationary does." - Richard Hammond
"Speed is just a matter of Money - How fast do YOU want to go?"-Mechanic from Mad Max-
If at first you don't succeed - Don't take up Skydiving!
- ThunderII KE7CSK
User avatar
F9K9
Mod K Elite
Mod K Elite
Posts: 6183
Joined: Sun May 30, 2004 12:26 pm
Location: London, Kentucky, United States

Post by F9K9 »

I found this site super for electrical and audio info for when Brule is asleep or at work :lol:

Because I am clueless with electricity!
[size=75][b]"For those who have fought for it, [i][color=red]FR[/color][color=white]EE[/color][color=blue]DOM[/color][/i] has a taste that the protected will never know."
[url=http://www.naxja.org/forum/showthread.php?t=73349]GUIDE TO SEARCHING. [i] (Some of the forum software is different but, it has helped me a lot.)[/i][/url][/b]
[b]"Those who don't know history are destined to repeat it." Edmund Burke[/b][/size]