relay wiring for LED light bar (1 Viewer)

[JamesR]

Hello All,
First, I tried the "search" option but I didn't see my specific question.
I am going to wire a 15 in LED light bar, 2 LED spots (front bumper), and 2 LED floods (rear bumper). And, some LED's in the rear cargo area. I am going to use 4 different relays.
87=load
85=chassis ground -
30=fused to battery +
86=switch on dash
My question is for post number 86 on the relays. I know that post goes to a switch (trigger wire). Can I wire all four relays to the same "hot wire" under the dash? Maybe the cig lighter? (I understand that this post is a low current draw post.)
If this is not a good idea, what would be better?
Thanks.

 

[TrickyT]

Relay terminals 85 and 86 are for the relay coil. Terminals 30 and 87 are for the relay contacts. The relay contacts get wired to fused B+ on one terminal (e.g., 30) and the LEDs on the other (e.g., 87), with the second wire on the LEDs wired to vehicle ground. For the relay coil terminals, one is wired to a different and much smaller fused B+ (say 3-5A) and the other to the dash switch, with the second terminal on the dash switch wired to ground. Of course this makes all the LED lights independent of the ignition switch. If you want to avoid the possibility of forgetting to switch off the lights every time you exit the vehicle, then instead of running the relay coils to a separately fused B+ circuit, just run them to a circuit that is only energized when the ignition is in the "engine run" position.

And, no offense, but all this has been covered in previous threads. You just need to search a little harder.

 

[JamesR]

Thanks TrickT,
I didn't take any offense. I guess I should have been more general in my search string.
I appreciate your reply.

 

[canman]

Relays still take power/ current to operate. You might want to check the current draw of all four relays combined. A buddy burnt up his truck good by using the cig lighter circuit to run a fridge and a bunch of stuff. THe wire gage on the cig lighter is pretty thin IIRC.

 

[JamesR]

Okay - thanks.
I have a hot wire run into my cab for the in-cab winch control. I could tie on to that one. It's a good size wire.

 

[JamesR]

Found the following info at Wire/Fuse Size & Relay explanations - JeepForum.com

 

[canman]

Found the following info at Wire/Fuse Size & Relay explanations - JeepForum.com

View attachment 1200618
View attachment 1200619

Good diagram, but in theory the circuits for the lights should be fused as well. The 80A fuse is too big for the power draw shown also. I used some double sealed relays for my driving lights that I pulled off a 4Runner I think. Lots of good stuff like that can be had at the wreckers for next to nothing incl OEM switches.

 

[JamesR]

I liked the diagram. I agree that the 80A fuse isn't the correct size. I thought I'd post the diagrams for a reference on what was done or to provide additional ideas.

 

[Coolerman]

Good diagram, but in theory the circuits for the lights should be fused as well.

They ARE fused in that diagram. The Master Power relay has a 5 amp fuse that is protecting the wiring from the Master Power relay Terminal 87 to the switches and on to each of the light relay coils Terminal #86 . One must assume the +12V keyed fed from the vehicle is taken from a fused source.

The 80A fuse is too big for the power draw shown also.

Nope! The 80 AMP fuse (true for ANY fuse used for WIRING) is there to protect the large wire from the battery to the fuse panel and has nothing to do with what the fuse panel powers. If that wire is say a 6ga wire (capable of passing 101 amps when used as Chassis wiring) then the 80 amp fuse is just the right size. The 80 amp fuse also allows for more circuits to be added to the fuse panel later without having to upgrade the feed wiring and fusing.

Not ragging on you, just pointing out an all to common misconception about fusing. Fuses protect the WIRE, not the device connected to the wire. If a device needs fuse protection it will be on/in the device and is usually MUCH smaller than wiring fuses.

 

[canman]

They ARE fused in that diagram. The Master Power relay has a 5 amp fuse that is protecting the wiring from the Master Power relay Terminal 87 to the switches and on to each of the light relay coils Terminal #86 . One must assume the +12V keyed fed from the vehicle is taken from a fused source.



Nope! The 80 AMP fuse (true for ANY fuse used for WIRING) is there to protect the large wire from the battery to the fuse panel and has nothing to do with what the fuse panel powers. If that wire is say a 6ga wire (capable of passing 101 amps when used as Chassis wiring) then the 80 amp fuse is just the right size. The 80 amp fuse also allows for more circuits to be added to the fuse panel later without having to upgrade the feed wiring and fusing.

Not ragging on you, just pointing out an all to common misconception about fusing. Fuses protect the WIRE, not the device connected to the wire. If a device needs fuse protection it will be on/in the device and is usually MUCH smaller than wiring fuses.

Your right. Thanks for pointing that out. Not sure why I said what I did as I thought the circuits were not individually fused. In theory you could probably get away with a 60A fuse in this case, but as you mentioned, there would be no room to grow. Correct with the fuse being sized for the wire, but sizing fuses and fuse types must also consider fluctuations in load/ current draw and reaction time to those fluctuations, but not relevant in this case with resistive loads.