hey,

so i have done some wiring with relays and understand how they work.

my question is about running aux driving and fogs on the front of my truck with the headlight switch.

i have a set of fogs, and a set of driving lights mounted/wired with relays. i have two on-off-on switches i would like to use.
switch 1: for fogs so i can have auto(with low beam) - off - on
switch 2: for driving lights so i can have auto(with high beam) - off - on.

i know i just need to trigger the relay with the switches, and with the auto function to just tap into the low beam and high beam circuit for my triggers . . .
BUT - i think the headlight wiring uses ground to complete the connection as opposed to 12v to complete the connection (i think 12v is constantly supplied, and the headlight switch just grounds when turned on)

i have found the wires which control low/high beam but am wondering if these will even work to use as the trigger for my relays . . .

i am hoping someone can chime in and help me out. in the meantime, i'll just wire the switches without the 'auto' functions as well as try a few searches on here . . .

tia,
jason

 

well i just tapped the wires and used them to trigger the relay. worked like a charm!

ended up answering my own question!

 

ok. stuck my foot in my mouth. i thought i had it figured but i don't!

the factory switches use grounds to complete the circuit and turn the lights on.

i can't for the life of me figure out how to wire this appropriately to turn the fogs on automatically with low beam, and the driving lights automatically with the high beams.

i tried a couple different ways to wire and flicking the switches but i couldn't get it figured out.

much help is appreciated!!!

 

I can't remember the wire color for the high beam tap but it's easy to find with a light probe. For some reason green or green trace comes to mind but don't quote me on that.

Everything works normal until I turn the lights off and the driving lights will come on. I beleive it's because of Mopar using a switched negative wire. through the DRL's.

The fogs are simple, just pop the fog relay apart and with a small piece of business card, put it between the contacts and they will stay on with high or low beams.

OR, does your truck not have factory fogs? If that is the case, any tap source from the lighting circuit will fire the fogs up.

Jeff

 

both sets of lights are aftermarket running off relays.

i have found both low beam and high beam wires under the steering column. i have tapped both and then ran a wire from each to a switch, when the switch is switched to that pole the fogs come on without lowbeam, and the driving lights come on without highbeam (as if the switch was switched to the other poles supplied with constant 12v)

does this make sense as i described it?

the constant 12v sides of the switch work fine and function as they should. but, the opposite sides (tapped from steering column wires) work just the same.

i am using 2x on-off-on switches (one for fogs, one for driving lights) . . .

 

I have always tapped the headlights right at the light itself. You then know the exact wire. Pretty hard to mess it up.

Honestly never tried tapping under the steering column so I can't help you there.

Jeff

 

i checked the headlight sockets and also found the matching wires in the steering column. once i found what i thought were the correct wires - i checked them with a piercing probe to confirm. when checking with a grounded piercing probe the lights actually come on so i know i have the correct wires tapped.

having the right wires is not my issue. my issue is getting the auxiliary lights to work as if they on the same circuit as the low and high beams . . .

 

So, if you've identified the positive for the headlight and high beam, tap into those and use them to energize one side of the coil in each respective relay. Run each other coil terminal to it's own switch, and from the switch to ground.
If it's a Bosch or Bosch knock off:
terminals 85 and 86 are for the coil: one to headlight that you want to activate your accessory light, the other to a switch and then ground.
Terminal 30 is the ground for the new lights.
Terminal 87, and 87B is positive for your new lights, fuse them for the appropriate load. If there is an 87A, it is on when 87 and 87B are off and vice versa. Clear as mud? Use a fuse between the positive and terminal 85/86, don't want a shitty connection to play havoc w your stock lights. Hope this helps.

 

not too clear on your 1st two sentences.

also, i have upgraded the factory headlight wiring with relayed harnesses. the switch still functions the same, but it just ttriggers the relays now which power the headlights.

not sure if that changes things.

 

Try to wire them like I did using 12g wire and relays......

https://www.dieseltruckresource.com/...d.php?t=292299

PM or call me (509-499-0252) if you have questions.

Oh yeah....beer helps :-)

 

Hey Dewd! You have most likely by-passed the DRL switch with your aftermarket wiring harness for the headlights? IIRC the schematic for the DRL has one, if not two, connections for the fog lights. Should you maybe be tapping into the live side of the DRL harness to control at least one set of your fog/driving lights?

Automotive lighting and wiring is all white smoke to me - I just remember this from hooking up my DRL bypass kit.

Cheers!

Mike

 

i could tap into the DRL if there is a fog control there, but then they would only function as factory and would not come on automatically with low beams. my truck does not have factory fogs either, so the credit card trick in the relay (missing in my truck) mentioned wouldn't work if i were to tap the DRL . . .

is that what you were getting at?

 

tanderson . . . not sure what you did will work for me. but i'll read it again and try to picture a diagram in my head.

BUT . . . your thread mentions diodes . . .

my problem is that the fogs and driving lights come on when the respective switch is flipped tot he pole tapped to headlight and high beam triggers - so essentially grounding out.

IF i were to place a diode inline of the 'tap' wire (not 'tapped' factory wire) i added to only allow current away from the factory wire would that work?

so esentially current could flow away from the factory wire, up the tap wire, and into the switch when in the applicable position . . . but not the other direction . . . think that would work?