GEN 2 Opinions/Input on wiring lights into the high beams.

[Droofe]

Wondering if there are any downsides or hurdles i haven't thought of for wiring 2 of my three pocket lights and a 40" BD onX6 light bar into my brights. feels like itd be nice to have a kill switch in the upfitter switch, but just be able to put my brights on when i want to use the light bar if the switch is on.

 

[4x4TruckLEDs.com]

LVJ Motorsports makes a relay system for this. I have it installed on my truck but have yet to do the high-beam trigger. My plan is to trigger my 4x LP9 Pros low beam modes when i do the highs.

Only reason I've not done this yet is i'm out of upfitters so I don't have a kill switch and I'd want a kill switch in there.

But I think it's a great idea. Especially since the stock LED Headlights are just terrible.

 

[smurfslayer]

@FordTechOne has repeatedly poo-poo’d this idea as ‘unwise’. I’ll try to recall from memory, but basically it can harm the BCM over time, possibly “bricking” it. That would suck.

The lighting system is much, much more complicated now than when many of us grew up around cars. it’s not just tying into a circuit, setting up a relay and hoping you have enough alternator to handle it.

Electrically, you would think it should work, pretty simply. You’re only tapping the high beam as a signal, which should be insignificant draw wise. FTO posted up a pretty detailed explanation on it in another thread and it boils down to - it’s not just about wire gauge and draw, it’s the BCM(? I think that was the module) oversight of the circuit.

 

[GordoJay]

@FordTechOne has repeatedly poo-poo’d this idea as ‘unwise’. I’ll try to recall from memory, but basically it can harm the BCM over time, possibly “bricking” it. That would suck.

The lighting system is much, much more complicated now than when many of us grew up around cars. it’s not just tying into a circuit, setting up a relay and hoping you have enough alternator to handle it.

Electrically, you would think it should work, pretty simply. You’re only tapping the high beam as a signal, which should be insignificant draw wise. FTO posted up a pretty detailed explanation on it in another thread and it boils down to - it’s not just about wire gauge and draw, it’s the BCM(? I think that was the module) oversight of the circuit.

The problem with tapping the high beam as a signal is that the relay draws a fairly significant current. Not a lot compared to the lights themselves, but substantial enough to be a problem. I'm not aware of any over-the-counter solution that uses transistors instead of a relay(or transistors to drive a relay). If you can find one, that would be the ticket, as current draw should be negligible.

 

[4x4TruckLEDs.com]

Relays don't use a "substantial" draw to trigger. That's why they are used everywhere.

I don't think you need to worry. I've never heard of anybody ever messing up any circuit on a vehicle using a relay.

 

[smurfslayer]

Honestly... the relay is just a switch. It’s powered direct from the battery, not the lighting circuit. The light circuit in this case would only be a trigger to the switch(relay). I think I raised this in the other thread, but I don’t have anything to counter what he said or any reason to doubt its validity. That and I don’t want to brick one of the crucial modules in my truck.

 

[smurfslayer]

Found it, here:

#24

hit up that post and ensuing advise from @FordTechOne
Really, that should be a sticky in the Gen2 lighting section.

 

[GordoJay]

Relays don't use a "substantial" draw to trigger.

From what I recall, it's enough to mess with the BCM. The BCM uses FETs to drive the lights. There are all kinds of fancy things that they can do in the BCM as a result, like putting a very tight tolerance on current draw to detect a bad headlight. I'll let @FordTechOne expand on that because I'm going from memory of one of his previous posts.

 

[4x4TruckLEDs.com]

Found it, here:

#24

hit up that post and ensuing advise from @FordTechOne
Really, that should be a sticky in the Gen2 lighting section.

Basically what I've been saying... you need to use a relay. The LVJ Kit is a complete relay setup.

Not only with regards to the BCM but with ANY circuit on your truck you should never just "tap" into something and power another source. YEAH, we all do it but you can't just do that.

Hell I'm doing it with my dash cam right now. I have it tapped in with a add-a-fuse tap on my power windows circuit. Occassionally the draw of my dash cam and the power windows is too much and the fuse blows (happened to me at an off-road event). That's from me closing the sunroof + 4 windows at the same time the dash cam is on. POWER overload.

But if you are going to trigger some extra lights to turn on with your highs, you need to use a relay to power those lights. In fact... I should really install a relay myself instead of a fuse tap because of the amperage draw on my dash cam. It's not like it's a small 1amp item that would be fine, it's got some decent draw.

 

[FordTechOne]

Relays don't use a "substantial" draw to trigger. That's why they are used everywhere.

I don't think you need to worry. I've never heard of anybody ever messing up any circuit on a vehicle using a relay.

I’ve seen it plenty of times. The draw from the relay doesn’t need to be “substantial”, it just needs to be enough to exceed the BCM’s pre-determined threshold for current draw. That threshold depends on the factory load that the FET is driving. Once the the threshold is exceeded, the BCM will set a DTC against them circuit. If the over current condition reoccurs, the BCM will shit down the circuit. If the fault continues to occur, the BCM will eventually permanently disable the circuit output.