wiring light bar harness

[kenwahoo Junior Member Find all posts View Profile Close kenwahoo]

Well, got a harness with the light bar I just bought. Just a chinese one but don't hold that against me. Trying to decipher wiring as relay is a generic 4 pin one without numbers but I think I've identified the pins anyhow. Lots of info on the net with many using the pin numbers on the relay. However as my relay has no numbers I need help as I think the harness, like all of them, are wired for positive switching. As the Prado is negatively switched the connections need to be properly done so that the light bar is connected only to the high beam and switchable. To do this, out of all the wires from the relay, I think what I have to do is connect:
- red fused wire to battery positive
- black ground to battery negative and light bar
- red wire to light bar
- white, in my case, goes to switch
- red from switch to positive high beam
- black from switch to negative high beam

Is this correct? Usually the red and black from switch goes to accessory but if it's going to come on with high beam it may as well be switched from there.

[Guest Close Guest]

The purpose of the switch is to have the light bar on or off when the high beam is on. Eg, in town, you can high beam someone to signal to other drivers that you are letting them through. But to have the LED lightbar go off at the same time would be blinding.

In rough terms, the control circuit should look like this
High beam -> switch -> relay -> LED lightbar

[kenwahoo Junior Member Find all posts View Profile Close kenwahoo]

Isn't that how I've described it? I think I've followed Ironman's diagram for negative switching

[Guest Close Guest]

Your switch wiring does not appear to go to the relay

[kenwahoo Junior Member Find all posts View Profile Close kenwahoo]

Ah, fair comment as I failed to mention that the wiring as I described is coming out from the relay. Does this make the difference? I edited #1 accordingly.

[Corigator Avid PP Poster! Find all posts View Profile Close Corigator]

Interesting. I have just bought a lightbar and was pondering the wiring. I drew up this diagram, which I think matches your thoughts for a negatively switched vehicle.

[kenwahoo Junior Member Find all posts View Profile Close kenwahoo]

I hope so. Problem is that the relay I have has no numbers outside or inside as I've opened it to look. All I have to go by are the colours of the wires and what they're attached to. Only thing to do is to hook it up but I wanted some confirmation that what I intend will work right. At the same time I'm getting a harness to upgrade the headlight wiring. So far I've only found one retailer who markets a loom which includes wiring for spotties. This is useful for someone who wants to upgrade headlight wiring and have decent loom for the spotties at the same time. His wiring diagrams are used for illustrations but the one email I sent for info was not replied to so I'm not impressed by that.

Digressing to looms, I note that there's a lot from China but most use 16 & 18 gauge wire although there are sets with 14 gauge. still in comparison, Piranha uses about 10 gauge so there's a huge discrepancy there. With the led light bars getting more powerful the current Chinese wiring looms are inadequate. My light bar is a 23" 300 watt. While I don't believe the circuitry in the light bar will produce 300w one still has to assume that it will and wire accordingly. Using too thin wire is simply asking for trouble and I'm on the verge of copying the loom I have using thicker wire so that it can cope. Loom came with the lightbar and was not separately bought. If I decide to make a loom then I'll give this one to a friend who has a 120w lightbar. Loom will be more than adequate for that. I think it'll be a long time before the chinese sell looms the quality of ARB or Piranha.

In the meantime I've learnt that the advertised dimensions of wire in one particular auto chain is all wrong. I got permission to take short bits of what is supposed to be 3mm, 4, 5, 6. When I put my calipers to them I lost 1mm in diameter for all of them. Basically paying more for less. I was surprised at the incorrectness for the whole range they carried. Maybe one is a mistake but all of them? Maybe other retailers are better but the lesson is to take care to measure before buying. Wire prices in Australia are not cheap and one can see why the looms are around $200. There's not much margin taking parts and labour into account. Very different in China as source materials cost a fraction of what they are here and that's why you can now buy 16 gauge looms for $10 - 15. Heck the Narva relay alone costs more than the whole loom.

Enough ranting for now. going to bed. see you all

[Guest Close Guest]

A true indication of wire sizes is AWG.

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

The power rating of the bar will be its theoretical power output.

Best to measure it first, you'll probably find it draws around 10A to 15A.

Cheers

[kenwahoo Junior Member Find all posts View Profile Close kenwahoo]

I think what I will do is to use the relay I already have and replace the wires to 10 or 12 awg except the switch one as this will carry the load, theorectical or not. Another thing to do is to fit a Deutsch or waterproof plug & socket as the light bar came with 30cm wire but bare ends. 30cm is a bit short and given that it's in front it's important to waterproof it. Problem is to get one that the wire can fit on. The thicker the wire the more expensive the plug. It's easy to forget that the cheaper plug/socket can only fit thinner wire and mayn't carry the load. Also want to replace the button switch to a rocker which can slot into one of the spare holes on the dash. Anyone know of a rocker that fits. The standard ones seem to be 2mm too wide. May need to get one from wreckers.

[Guest Close Guest]

The switch is not supposed to carry any load.

[kenwahoo Junior Member Find all posts View Profile Close kenwahoo]

I didn't mean that the switch carried the load. Meant that the wire size chosen is enough to carry any theorectical load. Thing is the wires to the light bar are only 3mm od so now I'm not sure of the benefit of upgrading the cable. Also, the length required from relay to light bar connection is about 1200mm.

Well it looks like I either replace all the important wires in the loom or get/make a new loom because the thickest wiring is only 16awg, sigh!! At the same time I'm looking at a new loom for headlights but I've only seen one combo kit that you can buy.

[kenwahoo Junior Member Find all posts View Profile Close kenwahoo]

Before I embark on making the loom I drew up a diagram. 2 hints I got from elsewhere regarding negative switching:
1. Power always on and negative used to switch on and off
2. Relay connections are 30 - battery power, 87 - spotlight, 85 - High beam feed & 86 - 12v common

Going to use a fuse block so that there's only one wire from battery positive. Someone like to examine my diagram and let me know if I got anything wrong. thanks. Deleted thumbnail and provided original pic. Click on it should give full size. Let me know if it doesn't as not sure if I did it right

[maulbeagle Senior Member Find all posts View Profile Close maulbeagle]

The picture opens up too small to view. For me at least. Not sure about others.

[Corigator Avid PP Poster! Find all posts View Profile Close Corigator]

Interesting. I have just bought a lightbar and was pondering the wiring. I drew up this diagram, which I think matches your thoughts for a negatively switched vehicle.

I found I needed to add a diode between the switch and the relay (86) to stop reverse current making the on light in the switch shine when I was on low beam even with the switch off. It seems that when the highbeam is off the negative side is still positive through the light, which triggers the on light. Works fine now. Negative switching is a pain in the ...