How to wire a relay

[whiteknight]

I see way to often people adding new high current circuits to there rigs with no relays to operate the device. This will lead to problems up the road and a unreliable electrical system.
Most aftermarket switches (rocker, toggle micro,etc) can usually only handle a max of a 10 amp load, after that you are causing damage to the switch. The idea behind having a relay installed is to take the heavy current away from the switch. This will allow much smaller gauge wiring to be done under the dash and keeps the heavy gauge high current wires out from under the dash where they do not belong.
An example.
A pair of small fog lights usually draw from 8 to 10 amps. If the lights were only run through a switch, the switch would burn out in a short period of time. By using a relay, you end up moving the heavy current through the relay and not through the switch. A normal 5 terminal relay will only draw about 0.2 to 0.3 of an amp to turn on. so that's only a max of .3 amps that is going through the switch. The switch will last a life time.
You can get relays that can handle a 30 - 80 amp load, very cheaply.

Most general purpose relays have a set of normally open contacts and a set of normally closed contacts and are wired internally as shown in the picture posted below. The two terminals that turn the relay on and off are (85 and 86), The terminal for your main power in is (30), and the terminal for main power out for a normally closed circuit is (87) . If you want a normally open circuit you would use (87A) instead of 87. Some relays reverse the 87 and 87A markings.

When wiring your electrical system. The correct way to wire things like fuel pumps, cooling fans, fog lights, nitrous controls, etc. Is to use a relay to control the circuit. This will save you a lot of grief up the road !

Attached image(s)

[Bowtie972]

This is also an easy and cheap way to improve your headlights, Buy an inexpensive relay at Auto zone ,

term 85 & 86.............. ground on one terminal and  on the other terminal 12V that comes  from high beam switch (tap into this wire and solder, dont cut it.   Liquid electrical tape works nice on these solder joints, at least two coats. Doesnt matter which one goes on which terminal.

term 30......12V power


term 87or N/O.............run wire from this term to wire that feeds low beams (again, tap into and solder)


Now when you activate the brights, the  low beams will stay on for twice the light, low beams will work  normal when high beams are off. This is great for trail rigs or daily drivers, cheap too!

Check a manual for wire colors or use a test light to figure out which wire to tap into.

[catfish]

cool figuerd i was doing somthing wrong, how do you git to the atached images i dont have a link or nothing on my screen

[TBigLug]

This is true, but you need to be careful. Sylvania's headlights are only rated to operate on 10-11 volts. Over on Oilburners, alot of guys were burning out their headlights when they went to a larger gauge wire and relay setup. The 13 volts from the lower resistance caused the Silverstars to burn out prematurely. Something to keep an eye on. Good info though.

[Bo Duke]

So what ur saying is my 4 off road lights going to one switch with no relay is a bad thing.....LOL

[TBigLug]

So what ur saying is my 4 off road lights going to one switch with no relay is a bad thing.....LOL

Nah, you've still got room for 2 more!

[Hammerlane]

So what ur saying is my 4 off road lights going to one switch with no relay is a bad thing.....LOL

No, it's not a bad thing..






Not until the fire starts !!!