Electrical Relay wiring help

Wayne Waldrep

Before I post a pic, do you have one of yours?
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Relay wiring vid. This video is good but it does not do what I have always understood to be one of the main purposes of relays. I've always seen them used to allow a thin gauge wire to be used to activate the relay. For example, in fog lights, you don't want full power running into the car and to your on/off switch. Using a relay would be like this if I can describe it correctly.....

Power from 12v battery to relay using heavy gauge wire (per needs). Heavy gauge wire to fog lights and ground from fog lights. This completes the heavy circuit. The last thing is the thin wire into the car to the toggle switch. This is not how this guy is using them.

Can one of you electrical wizzes (?) look at this vid and tell me what you think? He did a great job illustrating the use. It's a solid vid to me. But I'd like to know how to modify this to use the thin wire activation method. Sad to admit this but I've done this wiring job on my mustang fog lights and when I added a custom light bar on my motorcycle. My old brain is not retaining anything anymore. Beginning to think there's more wrong up there than before....lol. That's why I copy and paste these answers when they come. Off-site brain storage.....ughhh.

Thanks for the help.


View: https://www.youtube.com/watch?v=W2Mr2Zgv1Ck
 
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90sickfox

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86 and 85 are the low amp circuit. 30 and 87 are the carrier wires to the load. The relay can be triggered using 86 ( + ) or 85 ( - ). Fuse on wire going to pin 30. Most relays are rated for 30amps so a 30 amp fuse would be the largest.

I run all my relays with the trigger switch on the ground side 85 so I don't have extra positive live wires running inside the car. I actually just branch off of the wire feeding pin 30 and jump it to pin 86.

Pin 87a ( center pin ) alternates opening with pin 87. When relay is energized its open ( no voltage ). When relay isn't triggered its closed ( battery + ). This is with most relays. Some relays are wired to trigger 87a and 87 at the same time but those aren't your common 5 pin relay.
 
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Wayne Waldrep

Before I post a pic, do you have one of yours?
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Good answer. I need more info on the middle paragraph though... Sorry. That's the part I'm struggling with. Don't assume i know how to even spell electrackle. :D
 

Mustang5L5

Put lubricant all over the balls
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Relays typical use a solenoid to pull in a set of contacts to make/break the connection for your main power feed.

Here's a diagram that shows the internals of the relay. You have your Line (source) which is Pin 30, and your Load which is 87 (and 87A on a 5-pin relay shown below).

85 and 86 are your coil power and ground. This is what moves the amature to make/break connections between your load and your lines. This coil is very low current draw. Under 1amp typically but relays usually give this spec. Due to this low load, you don't need heavy gauge wiring for the coil. 18-22 will suffice. You can see wire size in the below diagram is smaller for the coil

I typically wire them like 90sickfox in which i'll tap off power nearby from something that has key on, or always on power, and then switch the grounds.
1643391699626.png
 
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limp

wrap a little cheese around it and its a done
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I know its less money to build one, but this place, ceautoelectric.com, has what I think is a nice Headlight relay kit #HRK2....
 
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Wayne Waldrep

Before I post a pic, do you have one of yours?
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Thanks. I have my fog lights on a relay already. Who knows how i did it a couple years ago. I'm going to untape it and see. I just wanted to get it in my head first. So i watched that video and it didn't jive with my thinking. That's why the questions.
I think on the fog lights i really only need a 4 pin relay, correct? I don't need the alternate power from 87a. I think i have it now. Like you both said, I'll run pin 85 inside the car with an 18 ga wire and break it with a toggle switch to chassis ground.... Correct?

So here's what i need answered and i think I'll be done.....
1. I only need a 4 pin relay.
2. Switched ground from pin 85 to toggle switch with 18ga into the interior.
3. How do i power the 3rd pin on the toggle switch to light the led?

And thanks to Mike for helping me with the USB wiring earlier! This is electrical problem 2...lol
 

7991LXnSHO

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Wayne, to add to 5L5’s always good info, some relays, like the one in the picture, are wired to be normally open (off without trigger signal) or normally closed (on without trigger signal).
See the two terminals in the right of his picture. If you have one of these dual purpose relays, you will use the NO, normally open circuit wire to power something. The NC is better for a kill switch or logic circuit setup like the headlight buzzer I have ready to install.
BA856D49-93F3-4F73-BE64-FE2351BF6FFD.png
 
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Mustang5L5

Put lubricant all over the balls
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3-pin toggle switches with led usually require 12v on the third pin and then you switch the grounds, or vice versa.

Need to see switch to confirm though. I am making an assumption here
 
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General karthief

wonder how much it would cost to ship you a pair
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There was a write up on the fog light fix that used the factory switch around here someplace, all this 'closed-on open-off' stuff can get confusing for non electrical back yard hacks.
I can follow a diagram though.
the fog light fix is on the list of things for the Junk Pyle.
 

Wayne Waldrep

Before I post a pic, do you have one of yours?
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I think i have it all set in my mind once again. Thanks for the help guys. Getting decent lighting back on the car is something i hope to work on. I got some of the ultra clear fogs from LMR a couple years ago. The inside metal just melted even with the supplied bulbs. Think I'm going back to some glass housings and 100w bulbs.
 
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7991LXnSHO

wanna catch the space herp
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There was a write up on the fog light fix that used the factory switch around here someplace, all this 'closed-on open-off' stuff can get confusing for non electrical back yard hacks.
I can follow a diagram though.
the fog light fix is on the list of things for the Junk Pyle.
Sorry if that was TMI. I assumed if someone can follow the surging idle checklist that the terminology for switches and relays should be easy enough to understand if not already common knowledge. Sometimes I read too much and do not type clearly enough,

The relays from Amazon are likely to be double function (NO/NC) with the extra terminal now like in the diagram. The basic horn and light relays from the FLAPS are still usually the single function, power to turn on relays. So those are the ones to use on lights, and the Heavier Duty ones for cooling fans.
 
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