High Beam Wire Size

@kapn ,

The AOB switch is grounded behind the dash, and the ground under the hood comes from the light bar and shares the ground location on the inner fender with the battery.

The schematic from AOB doesn’t show a ground connected directly to the relay so I did not do that. Should there be or am I misunderstanding your question?

For the trigger from the high beam bulb socket, used the side that showed no voltage on the meter when selecting high beams on the OEM stalk. After not being successful with that, I reversed the plug in case I was on the wrong wire and that didn’t work either.

Unfortunately, I can’t mess with it again until tomorrow but I picked up an autozone relay just in case.

The original relay definitely clicks and sends power to the light, just at the wrong time. When connected exactly as the AOB schematic shows, I get LED bar illumination with high beams OFF and no LED bar when high beams are on.

Would it be possible that the red wire from the bar is actually the ground and the black wire is the power? Or would that even matter?
Nothing makes sense to me at this point.

I’m so confused and I appreciate your help.

 

I reread the posts and see that I was wrong once I looked at the schematic. I kept thinking of a pos switched headlight. Sorry for all the confusion.

Let me reread again and study it.

 

The switch ground is often for just the illumination leds in the switch and has nothing to do with the accessories activated by the switch though sometimes power comes through the relay first and is grounded through the switch. Need to see a schematic to see which way they laid it out. For the light bar it could be as simple as switching the light bar from pin 87 to 87A on the relay or vice versa.

 

It’s a 4pin relay so no pin for 87a. Here’s the schematic that came with the switch.

 

ok, so if I was there I’d take wire 86 and check it for ground. Putting one lead on the pos from the battery and the other on that wire there should be no voltage showing on the meter. Then when the high beams are on, it should show 12v.

 

Ok I’ll give this a try shortly and report back. Thank you very much

 

My appologies, I hadn't reviewed the schematic. The switch ground is in fact only for the switch led(s). The red and green switch wires are the only ones involved in the lighting circuit. With the diode there in that orientation current can only flow from the switch to the relay which happens only when the wire connected to pin 86 is also connected to ground so it sounds like you have the wrong headlight wire on pin 86. If the light bar only comes on with low beams then the low beam wire is connected to 86.

 

Thanks @bagleboy , I’ll get a meter on it shortly and report back. I appreciate your help.

 

You're welcome, just needed some sleep and to look at the circuit. The relay is activated when the light bar switch current has a path to ground. Follow the path from pin 86 to ground through the main headlight switch and you'll see what I mean. If the lights come on with low then that's the wire you have connected to 86.

 

Ok here’s what I just found. With red lead from meter on pos battery terminal and black lead testing drivers side high beam socket, with high beams OFF, both sides of plug show 12v. When high beams are switched ON, one side has 12v and the other shows no voltage.

That seems backwards to me.

If I put black lead of meter on the negative battery terminal, and red lead from meter on high beam socket, high beams off no voltage on either side of the plug. High beams on, voltage on one side of the plug and none on the other.

 

Ok, so it sounds like the high beams are not negative switched.
You need to use the diagram from the positive switched setup. Pin 85 should be grounded and 86 should come from the high beam wire that gets positive power when they are on. It will go through the dash switch where you can interrupt it to be off when just using high beams in town and switched on to link the light bar trigger to the high beams.

 

Wow. Ok I’ll give this a try and let you know. Thanks man

 

Don't 3rd gens have two bulbs and two plugs and both are on with high? You're not looking for a 12v source but a particular path to ground with the high beams on. If there are two bulbs then each socket has a hot wire and a wire that grounds through the headlight main. You want the grounded wire for the high beam bulb when the beams are on high. That's a continuity test not a voltage test.
Locate the high beam bulb socket and test it for voltage. Then test the wire that isn't hot for continuity to ground with the high beams on. That should be the one connected to pin 86 to get your light bar to come on with high beams only.
I'm going by what I've discovered in the past 20 minutes or so searching 3rd gen bulbs so I may be full of shit but if there are two bulbs each with its own reflector then it should be easy enough to see which one comes on with high(the inboard or outboard one) and go from there.

 

You're making this much harder than you need to.





and done.

 

Damn. This does look easier. I’ll give it a try. Thanks.

 

Isn't this for anytime lights rather than high beam only?

 

And you don't end up chopping harnesses up in your new truck.

 

Not if your Add-a-Fuse is on the Highbeam fuse shown. 12v trigger on relay is only there when the highbeams are on.
You can also Add-a-Fuse to the other lamp if you want another set of lights controlled by the highbeam circuit.
Or use the low beam if you want power with headlights, or pick another for switched power, or an empty slot for constant..
Use your meter to check how they are powered and go for it.

 

That’s the air-on-board switch schematic for “positive switched vehicles”

We are all in agreement that this truck is in fact positive switched at this point?

 

Cool, always happy to learn a bit more. I'm using a bussman for most additional fuses/relays but this is a good way to key them to the headlights, certainly better than tapping the harness.