DIY Relay Box

[jcx03]

Recently started adding more and more accessories and everything is running with premade wires with switches & fuses with relays.

Watched the Overland bound videos and was super confused at first, but slowly, everything made more and more sense. Hoping someone can double check my work.

Does this look correct?

Also, with the negative ground, can i turn the accessory on with the car off.

edit:updated image

 

[Flipper]

Your wiring is incorrect. You have no switch to turn the relay on and off. All a relay is it a switch that can handle a large current draw that is activated buy a switch in a low current application that couldn’t handle the higher current of the draw of the lights. The switch would be before the relay not after it. Any questions give me a shout, I will be glad to help.

 

[jcx03]

Your wiring is incorrect. You have no switch to turn the relay on and off. All a relay is it a switch that can handle a large current draw that is activated buy a switch in a low current application that couldn’t handle the higher current of the draw of the lights. The switch would be before the relay not after it.

I'm trying to follow a negative ground setup, like Michael explained recently. Am I just completely wrong? The way I understand it is that, the positive is always connected, but when the switch in my dash flips, it connects the ground to the body of my car, and then completes the circuit for the accessory.

His diagrams are here, but don't show how to do the switches.

https://overlandbound.com/downloads/fuse1.jpg

https://overlandbound.com/downloads/fuse2.jpg

https://overlandbound.com/downloads/fuse3.jpg

 

[M Rose]

Pins 85 and 86 are the relay switch. Pin 86 is most commonly the ignition hot, pin 85 goes to switch them to ground. Pin 87 goes to the hot side of your accessory, pin 30 goes back to fuse box.

 

[jcx03]

Pins 85 and 86 are the relay switch. Pin 86 is most commonly the ignition hot, pin 85 goes to switch them to ground. Pin 87 goes to the hot side of your accessory, pin 30 goes back to fuse box.

I'm very sorry, but I think my set up is different here as I tried to follow @Michael video. Still a tad confused as I'm filling the gaps like the 5 pin switch.

 

[jcx03]

slightly updated now. I believe on the switch, terminals 2 and 3 switch connect when the switch is flipped.

@Flipper can you check this?

when the switch is pushed down, the ground connects terminal #2 and #3 in the switch, and completes the circuit for the relay at terminal #85. Thus allowing the relay to connect #87 and #30.

 

[M Rose]

It’s still wrong...

first let’s talk how a relay works. A ray is an electo-magnetic switch. It’s function is toturn a low amperage source to a high amperage source. Low ape rare side Is the election-magnetic coil on pins 85 and 86. The high amperage side is pins 30, 87, and 87a. When there isn’t any voltage applied between pins 85 and 86, you will have continuity between pins 30 and 87a, when power is applied to pins 85 and 86, the magnetic coil is energized causing the high voltage circuit to close on pins 30 and 87 thus continuity between pins 30 and 87.

so for your purpose, 85 goes to a positive source, pin 86 goes to your switch negative output, switch input is ground. Pin 30 is powered by the fuse box, and pin 87 goes to the accessories.

 

[M Rose]

It looks good... other than a simple question... do your switches have a single light inside them or a double? If double, one light comes on when you turn the switch on, and the other comes on with the headlights.

 

[EXPO_D1]

slightly updated now. I believe on the switch, terminals 2 and 3 switch connect when the switch is flipped.

@Flipper can you check this?

when the switch is pushed down, the ground connects terminal #2 and #3 in the switch, and completes the circuit for the relay at terminal #85. Thus allowing the relay to connect #87 and #30.

that circuit will work. i see no concerns. your circuit is fused and controlled by a relay. be sure to use quality relays that are rated for the load your going to be controlling.

 

[Prerunner1982]

Also, with the negative ground, can i turn the accessory on with the car off.

Yes it would except the light inside the switch would not come on to tell you that the accessory has been turned on.

 

[Michael]

Hi guys - I have not reviewed the modified diagram above but want to explain my wiring diagram - when you see the black wire off terminal 85 to "accessory switch" in the "fuse2" image, all that means is that the black wire goes in one side of the switch, out the other, then to a solid ground. This would be for a simple, non-lighted switch. If you were to simply touch that wire to a ground, the accessory would come on.

 

[jcx03]

It looks good... other than a simple question... do your switches have a single light inside them or a double? If double, one light comes on when you turn the switch on, and the other comes on with the headlights.

Thanks for reviewing it. I appreciate it!

My switches have double. Looks like I'll have to wire pin 7 to headlights, but if I did negative ground (like the diagram), it looks like I need to have pin 8 go to either my accessory.

I must ponder on this, as I currently have a few switches from kits I purchased previously.

 

[M Rose]

I’ve been messing with these switches on a negative ground system... I got the lights to work with the headlights, but can’t get them to work when the switches come on....

 

[jcx03]

I’ve been messing with these switches on a negative ground system... I got the lights to work with the headlights, but can’t get them to work when the switches come on....

Yeah it looks like it's counter intuitive if I want it to work properly as it has to route back to the relay.

Do you happen to have a rear setup as well? I want to install this and a few other lights on the roof + lift gate of my car, that will be easier route to the back of the car.

Looks like I need to do this twice essentially.

 

[slomatt]

Just to clarify, almost all cars are "negative ground" since the negative terminal of the battery is connected to the body, causing the entire body to be at ground potential.

I think what Michael did is switch the negative side of his loads instead of the positive side. In other words, he connects fused +12v DC directly to the load and then puts the switch between the load and the ground. Can anybody speak to the benefits of this approach? To be honest I can't think of any, but it does seem like asking for problems since if any part of the wire between the load and the switch shorts to ground (and remember almost all metal in the car is grounded) then the load will turn on. With a positive switched load if the wire between the switch and the load grounds out nothing happens.

 

[M Rose]

Just to clarify, almost all cars are "negative ground" since the negative terminal of the battery is connected to the body, causing the entire body to be at ground potential.

I think what Michael did is switch the negative side of his loads instead of the positive side. In other words, he connects fused +12v DC directly to the load and then puts the switch between the load and the ground. Can anybody speak to the benefits of this approach? To be honest I can't think of any, but it does seem like asking for problems since if any part of the wire between the load and the switch shorts to ground (and remember almost all metal in the car is grounded) then the load will turn on. With a positive switched load if the wire between the switch and the load grounds out nothing happens.

Actually the opposite happens... if you ground out high voltage side nothing happens, if the low voltage side shorts out then the accessory comes on and tells you where the problem is. With the relay actuating the positive side, and the switch shorts to ground you have a fire, blow a fuse, or both, if the high side shorts out then sparks and smoke for sure.

 

[jcx03]

I’ve looked at all the panels I’ve wanted to get, and switches. I may go with doing conventional switching.

 

[slomatt]

Actually the opposite happens... if you ground out high voltage side nothing happens, if the low voltage side shorts out then the accessory comes on and tells you where the problem is. With the relay actuating the positive side, and the switch shorts to ground you have a fire, blow a fuse, or both, if the high side shorts out then sparks and smoke for sure.

Hi Mike,

Can you clarify what you mean by "high voltage side" and "low voltage side"?

The diagram in the original post shows +12v from the battery going through a fuse and then to both the switch (30) and coil (86) terminals of the relay. The other side of the coil (85) is I assume connected to ground through the switch that controls the relay. The other side of the switch (87) connects to the load and then to ground.

My comment was that given that the chassis is grounded on most cars it is much easier to short a wire to ground than it is to short to +12v. In the diagram there are multiple things that can happen if a wire gets grounded out.
1. If the wire from the battery to the fuse grounds then you get sparks and perhaps a fire.
2. If the wire from the fuse to terminals 30/86 grounds then you blow the fuse.
3. If the wire from 85 to the switch grounds the load turns on.
4. If the wire from 87 to the load grounds then then nothing happens, until the relay is activated and then you blow the fuse.

#3 is the state I'd worry about. Personally I don't want a load to turn on if there is a short to ground since I might not be near the truck or I might not notice it while driving.

I suspect Michael used this setup since it can save running one wire to the switch. If you were to switch the positive voltage to the relay's coil then you'd need two wires to the switch, one with +12v and one to the coil. In a negative ground setup you can just run one wire from the relay to the switch, and then ground the other switch terminal anywhere on the body. The tradeoff is the issue in #3.

 

[M Rose]

The high voltage side of the relay is pins 87, 87a, and 30.
low voltage is 85 and 86...

Actually high and low voltage is the wrong wording.... it’s actually high and low amperage.

 

[slomatt]

Ok, I think I understand what you are saying. You are calling the coil side of the relay the "low amperage" side and the switched side the "high amperage" side. Thanks.

The coil side is a low current circuit that uses an electromagnet to switch the high current side.