Cabin Fuse Box - 7.5A Tail for powering BD S8 Backlight

Thanks a lot for the explanation. So the backlight tail fuse tap would have three wires on one side. What would be an appropriate fuse size? The 30” pulls 1.8A and 40” pulls 2.7A I believe — I currently have a 5A fuse in.


To confirm, the 12V source wires from the light bar and ground will be taped off? Does the switch ground need to be connected to at least one of these to close the switch illumination circuit?

 

Well the coil(s) don't even need an amp to close. The only concern is the fuse from the battery to the relay to the Light Bars and you have that covered.
For the switch to dim with the rest of the dash switches the switch ground needs to tap into the beige wire of your nearest switch.

 

Do you info on the draw of the backlight(s) LED's?
Once you tape off the wires, visualize the circuit this way:

The fuse at the battery will juice the Light Bars only.
The add-a-fuse the amber backlights and switch to relay coils.
Even this:

Simplify even more the install. 4 wires to the add-a-fuse butt connector.

 

It will be around 4.5A for both light bars. So if I finally understand this, the circuits to the switch will remain separate and the light bars won’t cross each other. They would only be connected at the amber backlights, but that is all good now as I know that works as intended.

It sounds like I would still need the switch illumination harness to separate the switch illumination circuit.

 

There will only be 2 wires towards the light bar relay from the switch. The rest get taped off.
The switch will get powered by the TAIL tap.
The TAIL tap will get 4 wires crimp. 2 for the Backlighting, 1 for the Illumination (+) and 1 to provide power to the relay coil(s) wire.
The switch illumination (-) is tapped into the nearest beige wire to the added switch you are installing.
5 amp fuse is fine.

 

Thanks Caribe! I'll try this solution out and report back when I can.

 

Reporting back!

I finally got a chance to re-wire, and I modified your diagram with splitting the 4-way crimp into two.

The funny thing now is that the amber led bar would only turn on if the white led bar is also on. White led bar goes on independently, however.

Still waiting for a warranty replacement for the dual switch; hopefully Caliraised comes through. My hope is that all will work properly once I get a replacement switch.

 

So you have an amber and a white bar and both have amber backlight?

 

Correct. I also confirmed that these amber backlights light up even with the relays are disconnected. So it seems like the amber backlights are wired direct from the light bars.

 

More like a direct power from the fuse coming from the battery. Or you tap the orange coming from the fuse not to the light bar...

 

2 wires to amber, one is always powered. It needs to be snipped and tapped off, the other one is the one to the dual butt connector on the tail add a fuse. Energizes the backlight when Tails are selected.

 

Like so...

 

This is practically what I did, except the switch illumination (+) and 12V source was tapped together to P/OUTLET2.

 

Correction: the harness only uses a 4-pin relay. Sorry for the confusion, and this likely changes some things in the wire schematics.

When I was tidying up the wires, I disconnected the relay from the entire harness but left the fuse tap for amber backlights in. The amber backlights remained powered, which makes me think that it only shares the same ground as the main lights but does not go through the 4-pin relay.

Hmm there is only one (green) wire to the amber, as the harness only has four (black for ground, red for 12V source, green for backlight, yellow for relay) wires available. So far I have taped black and red off, with green tapped into the tail fuse and yellow connected to the switch.

Strange that for some reason, the amber led bar is slaved to the white led bar. Really need to get a replacement switch.

 

Update: everything finally works as intended! See pics below:



Essentially what's causing the issue is me mistaking the red switch wire as the switch power -- a pinout diagram nor proper wiring diagram was not provided by Caliraised and I don't necessarily know or have the equipment to test the switch wires.