Wiring aux light bar to high beams

drodio

"Vader" • 2020 170" Crew 4x4
@hein you seem like one of the electrical gurus on this form and I’m hoping you (and others!) might have the patience to walk me through some electrical questions, which is definitely my weak point.

I recently got an Aluminess modular roof rack w/ a 52” light bar (just bought a cheap Niilight one for now... LMK if you think that was a mistake. Seemed like the difference between $100 vs. $500 or even $1k). Obviously the light bar has a red positive wire and black negative wire, which I’ve run through my roof and into my van (drilling holes in the roof of a brand new 2020 Sprinter was definitely a bit of a harrowing experience).

Now, what I’d like to do is power it up so that:

1) There is an aux “on / off” switch for the light bar
2) When the aux switch is in the “on” position, the light bar will light up when the high beams turn on
3) When the aux switch is in the “off” position, the light bar stays off when the high beams turn on
(I don‘t think I’ll need any scenario where I can turn the light bar on w/o using high beams, but tell me if you think I should account for that).

I bought a 6 gang bank of aux switches, so I’m ready on that front. Now I just have to figure the rest out.

I searched the forum and found results like this one, but those posts assume that the reader actually knows what he’s doing, which is definitely not the case with me!

So I’m hoping we can take this step by step. My specific questions are:

1) The LED bar comes with a 40a relay, which I’m assuming I can use. It’s got two sets of red+black wires – one goes to the battery, one goes to the light. So far, so good.
2) It also come with a switch with three wires: blue / white / black. My plan is not to use the stock switch that came with the light, but to use one of my 6-gang switches. I assume I can figure out which wire goes to which part of the switch (although if you have any ideas, LMK).
3) But here’s what I don’t really understand: Where/how do I wire this into my high beams? I need to somehow interrupt the wires in point #2 above so even if the aux switch is in the “on” position, it doesn’t actually turn the LED bar on unless the high beams are on. How do I do that? And by “how” I’m hoping you can be really specific — do I tap into a wire under the dash somewhere? Or in the engine compartment? Etc.

Thanks for helping an electrical n00b with what I’m sure are some very basic questions!!!

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RVBarry

Well-known member
Where/how do I wire this into my high beams?
Hi, the VS30 with LED headlights only has a CANBUS signal for the high beams.
If you have the PSM option, you might be able to use it, otherwise one of the highbeam devices from
Is needed.

See also
 

drodio

"Vader" • 2020 170" Crew 4x4
@RVBarry ok this is a helpful start! I don’t have the PSM option, so the CANM8 looks like the way to go. Anyone know of a US distributor?

And then... how exactly do I install this thing?

72713C11-D740-46E4-9451-DAFC3EF3CE9D.jpeg
 

drodio

"Vader" • 2020 170" Crew 4x4
@avanti I saw your excellent post on CANBUS hacking — quick question that I didn’t see referenced in your post: where exactly is the CANBUS located in a VS30?

I think I’d connect one (or two?) wires from the CANM8 above into the CANBUS, correct?
 

avanti

2014 GWV Legend 3500 I4
@avanti I saw your excellent post on CANBUS hacking — quick question that I didn’t see referenced in your post: where exactly is the CANBUS located in a VS30?

I think I’d connect one (or two?) wires from the CANM8 above into the CANBUS, correct?
Yes, always two wires (CanHi and CanLo) on a CANbus connection. It uses "differential signaling", meaning that the bits are encoded as the difference between the two.

I know nothing about the VS30. Sorry.
 

autostaretx

Erratic Member
The CANbus wiring will always be fairly small-diameter (gauge) wires, running as a "twisted pair" ... two wires spiralling along.

They're hard to see in this photo, but the violet/white and associated violet wires are probably the CANbus.

CANbusDisconnectRevealedVS30.jpg

The T1N Sprinter had (at least) TWO CANbus systems ... one for critical engine components, the other for "the lesser stuff"

If you look at this 2007 wiring diagram, the "Computer DataLines Circuit" (figs 11 and 12) are the CANbus(es).
They have two separate busses: CAN B and CAN C

((that wiring diagram suggests that the "maybe" green pair is the CAN C pair))

--dick
 

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