High Beam Wiring Driving Lights

[Defconxzero]

Hi All,
I'm trying to wire in Aux Driving lights with the High beams as shown in this diagram as ive done with other vehicles in the past

I used the maverick wiring diagram to determine the White wire on the drivers side is the High beam wire,

However when I tried to use the white wire as my trigger source, i found that it was Hot at all times! high beams on or off, that white wire is always hot, so when i tapped into it, my driving lights would stay on all the time.
How can this be!?
The only thing i can think of is that the small brown wire on pin 13 (on circuit VDN13 , coming from the BCM) is a modulating/control signal telling some circuitry relay inside the headlight to then use the high beam white power wire when the high beams are activated....?
Does this sound right, can anyone confirm or shed some light?
I also traced the BCM high beam signal wire from the BCM to the BJB and tapped into that and THAT is always hot too!!? wtf. anyone have any ideas?

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[Darnon]

The BCM messages the headlight module (in each lamp assembly) via the Local Interconnect Network (LIN) to turn high beams on/off.

 

[Dmat]

Everything has a module now. power is always supplied to them and another signal tells the module what should be on or off. Its no longer a wiring being powered or not.

 

[Defconxzero]

Thanks for the replies. I’ll try something else

 

[Darnon]

I don't recall off the top of my head if the fog lights can be set to operate with the high beams only.

Edit: Nevermind, I see from your post in another thread you already have fog lights on an F-150 switch.

 

[Oscarcat]

Hi All,
I'm trying to wire in Aux Driving lights with the High beams as shown in this diagram as ive done with other vehicles in the past

I used the maverick wiring diagram to determine the White wire on the drivers side is the High beam wire,

However when I tried to use the white wire as my trigger source, i found that it was Hot at all times! high beams on or off, that white wire is always hot, so when i tapped into it, my driving lights would stay on all the time.
How can this be!?
The only thing i can think of is that the small brown wire on pin 13 (on circuit VDN13 , coming from the BCM) is a modulating/control signal telling some circuitry relay inside the headlight to then use the high beam white power wire when the high beams are activated....?
Does this sound right, can anyone confirm or shed some light?
I also traced the BCM high beam signal wire from the BCM to the BJB and tapped into that and THAT is always hot too!!? wtf. anyone have any ideas?

I don't operate on your level of knowledge [or bravery] but did the white wire show as hot because of the delay feature that keeps the headlights on after shutdown? You tested it before the delay turned it off? Just a wild guess on my part.

 

[Silver23]

Hi All,
I'm trying to wire in Aux Driving lights with the High beams as shown in this diagram as ive done with other vehicles in the past

I used the maverick wiring diagram to determine the White wire on the drivers side is the High beam wire,

However when I tried to use the white wire as my trigger source, i found that it was Hot at all times! high beams on or off, that white wire is always hot, so when i tapped into it, my driving lights would stay on all the time.
How can this be!?
The only thing i can think of is that the small brown wire on pin 13 (on circuit VDN13 , coming from the BCM) is a modulating/control signal telling some circuitry relay inside the headlight to then use the high beam white power wire when the high beams are activated....?
Does this sound right, can anyone confirm or shed some light?
I also traced the BCM high beam signal wire from the BCM to the BJB and tapped into that and THAT is always hot too!!? wtf. anyone have any ideas?

according to your posted diagram the white or grey/blue wire should work.
Either your diagram is wrong or you tested the wrong white wire.

 

[Darnon]

according to your posted diagram the white or grey/blue wire should work.
Either your diagram is wrong or you tested the wrong white wire.

Or, as mentioned, it's not as simple as 'wire has voltage, light turn on'.

Service manual description of operation:
When the BCM reads a request for the high beams, it sends a message through the headlamp LIN circuit to the LED control module inside each headlamp assembly. The LED control module then provides the proper voltage to the high beam Light Emitting Diodes (LEDs) in each headlamp assembly.

 

[AutobahnSHO]

dang computers!

Of course everything was simple way back when, but gas mileage/power were both not as good pre- digital...

 

[Silver23]

Or, as mentioned, it's not as simple as 'wire has voltage, light turn on'.

Service manual description of operation:
When the BCM reads a request for the high beams, it sends a message through the headlamp LIN circuit to the LED control module inside each headlamp assembly. The LED control module then provides the proper voltage to the high beam Light Emitting Diodes (LEDs) in each headlamp assembly.

If that is the case, the diagram that was posted is wrong, like I said.
I've read the headlamps are different on different trim levels, at least the Lariat IIRC. My guess is that diagram is for a different trim than the OP's truck.
Or, of course, not even a maverick diagram. Oops.

 

[Darnon]

If that is the case, the diagram that was posted is wrong, like I said.
I've read the headlamps are different on different trim levels, at least the Lariat IIRC. My guess is that diagram is for a different trim than the OP's truck.

How is the diagram wrong? If the BCM is energizing the High Beam FET and thereby closing the Enhanced Exterior Lighting Relay at vehicle start then that's all still accurate. The difference is the meaningful part--energizing the LED arrays themselves--is occurring within the headlamp assembly.

 

[Silver23]

How is the diagram wrong? If the BCM is energizing the High Beam FET and thereby closing the Enhanced Exterior Lighting Relay at vehicle start then that's all still accurate. The difference is the meaningful part--energizing the LED arrays themselves--is occurring within the headlamp assembly.

The diagram shows 2 different wires running from the fuses in the "battery junction box" to each headlamp.
It shows the headlamps as seperate from the battery junction box. It also shows seperate connectors on the wires to each headlamp.
Does it look like the battery juction box, the relay in it, and the headlamps (left and right) as one piece to you in that diagram?

Anyway, It looks like the OP was testing the wrong wire and/or the diagram is wrong.

Oh, and also I don't know where 'at vehicle start' came from? These are high beam headlamps.

edit: I don't doubt the discription of operation you posted is wrong, it just confirms the diagram posted is wrong.

 

[Darnon]

Oh, and also I don't know where 'at vehicle start' came from? These are high beam headlamps.

Again, you're getting hung up on the part that the switching is happening within the headlamp assembly itself. So the high beam wire into the headlight can be energized all the time, but that doesn't mean the high beam itself is on.

Pretend the diagram looked more like this

When the BCM receives a message to turn on the high beams it in turn sends a digital command over the LIN bus to the headlamp pin 13. The headlamp assembly activates a MOSFET to complete the circuit of the incoming power on Pin 8 through the high beam LED array thereby illuminating it.

 

[Silver23]

Again, you're getting hung up on the part that the switching is happening within the headlamp assembly itself. So the high beam wire into the headlight can be energized all the time, but that doesn't mean the high beam itself is on.

Pretend the diagram looked more like this

When the BCM receives a message to turn on the high beams it in turn sends a digital command over the LIN bus to the headlamp pin 13. The headlamp assembly activates a MOSFET to complete the circuit of the incoming power on Pin 8 through the high beam LED array thereby illuminating it.

I see exactly what you are saying. But the diagram doesn't look like that.
That diagram posted before looks like the BCM is controlling the highbeam with that relay.
But I see now what you mean, that relay powers the whole lamp assembly not just the highbeams. Is that what you mean? That makes sense.

 

[Darnon]

I see exactly what you are saying. But the diagram doesn't look like that.
That diagram posted before looks like the BCM is controlling the highbeam with that relay.
But I see now what you mean, that relay powers the whole lamp assembly not just the highbeams. Is that what you mean? That makes sense.

That is just for powering the high beam. The low beam (and DRL on Lariat) have their own power input circuit.

The diagram doesn't show what's happening within the headlamp assembly because it's irrelevant; it's not serviceable. As long as its getting power, has ground, and is talking to the BCM it should Just Work.

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