Basically the relay used to power LED lights, well any lights for that matter, can have multiple triggers. This is called the control wire. PIN 86
The control wire that sends a signal to the relay to close the circuit and send power to the connected light can be from either a switch and/or another wire say like your reverse lights, trailer reverse light etc...

I have my LED bar in my grill on a switch to turn on whenever I want without the car running. I also tapped the high beam wire to also trigger the relay so when I hit my brights the LED bar comes on too.. So this relay has 2 trigger wires going to the relay and when either is activated it "starts" the relay.

A relay is a normal open circuit that is holding battery power away from the load (lights) until another wire energizes the magnetic open gate and completes the circuit allowing battery juice to then flow to the lights as normal.

That is the basics of a 4 pin auto relay.
1 pin is ground--- PIN 85
1 pin is power from battery---PIN 87
1 pin to lights or accessory needing power. PIN 30 (open circuit so no juice flowing)
1 pin is a "trigger wire PIN 86 with very small voltage just telling the relay to turn on and close the open gate for juice to flow direct from battery to lights (load)"

That trigger can be from a manually pressed switch, or any wire that has 12v power like reverse light, dome light, door open switch etc.....
When using 2 trigger wires, like manual in cab switch and reverse lights, its good to use a Diode to keep power from coming from your manual switch wire and back feeding to your other trigger wire which could be your reverse lights. Radio Shack carries them and they essentially a one way valve for power to only travel one direction...to the relay.... The drawing is an example of an ideal set-up to protect your OEM wiring and correctly use a relay.

Its not very technical but its the basics of a relay. The idea is to leave the heavy power load coming straight from the battery to your desired accessory and not through existing wires that may or may not can handle the extra amperage you're pulling through it to power your lights. Small LED's have small amp draw so using existing wires to power devices without a relay is possible.

Think of it as a little gremlin living inside the relay. In one hand he is holding an extension cord connected to the wall with power (battery), the other hand he is holding a plug to connect to the extension cord that will turn on something.
The gremlin holds them apart, say about 6" so they are not connected. Then you take a small taser. (control wire from in-cab manual switch or reverse light, head light, dome light) and taser him in the butt and he says ouch and quickly connects the two cords he was holding apart together and your device suddenly turns on. Turn of the taser and he relaxes and unplugs the two cords and turns off the flow of electricity. He may cry a little but its his job and he does it consistently.

And for the record no gremlins were harmed in this example of a relay.




Make sense
Danny

 

Thanks. Thats pretty much what I thought. Its been a while since I have wired one in.

So before I wire in the relay I was going to see how many watts the lights pull to see if the stock wire/fuse will hold it.

I know the cubes are 18w a piece. I am not sure about the LED reverse bulbs. I bought them here:
I am guessing they don't draw much.

 

So during my Google search I found that a 15 amp fuse will hold around a 180 Watts. I am not sure what my reverse light led bulbs are using wattage wise but along with my new led lights I am guessing I will be well underneath that number. So I should be able to safely wire into the reverse light power with no relay.

 

I'm running these, they're good for me for backlighting and for plowing snow.

https://www.superbrightleds.com/more...car/1701/4011/

 

Sounds like you will be fine.... The fuse of 15 amp is enough (Watts/Volts (12.5)= amperage)..
The wire gauge is also something to consider when factoring if the diameter can carry the amperage load when everything is turned on. I assume if the circuit has a 15 amp fuse then wire gauge is likely 16-18 which is good.

You can also add LED reverse lights in place of your halogen versions. This will further reduce your total amperage load on that circuit with all 4 reverse LED's running at the same time.
Enjoy your lights.

 

Thanks for the reply. My reverse lights are already LED.

 

Well I got them installed this afternoon. Cutting into the bumper was a little nerve wracking but I measured multiple times. I tapped into the reverse wire going to the trailer harness. Easy peasy.

 

Thank you for all the recommendations on the Philipps bulbs folks. Just popped them in this afternoon and tried them out once it got dark. They are AMAZING!!!

 

Ok so I may have a little issue. Today when backing up I noticed a warning in my dash. Check rear park assist. Yesterday when I installed the lights I tapped into the trailer plugin wires and utilized the middle wire labeled reverse lights.

After the install I checked and lights and parking assist was working as I could hear it beeping. Could I be robbing that system or overloading it due to the wire I tapped into?

Backing it up again an hour or so ago, it worked fine. Then all the sudden the warning came on again.

Thoughts?

 

Look back in this thread. Some other guy had the same issue with his backup sensors throwing false warnings.