Headlight electrical help.

[juicedcummins]

I just finished installing fog-lights in the factory holes on my auto.

They question is I want to hook them to the brights through a relay and cannot seem to find a switched pos on the bright side of things.

I also have it wired to a switch with dioed's for manual operation.

This truck also has drl's and a bright-box.

Any info would be greatly appreciated.

 

[wtrenholm]

In looking at the wiring diagrams, the OE foglights have a relay in the PDC under the hood.



Also, all switching is done on the ground side of the circuit, the head/fog lights are supplied power and the switches just control current to ground.



I looked at my '01 (without DRL) and I have all four terminals present in the PDC where the relay would be and the open harness with the correct color wires hanging behind the front bumper. I also have power to one terminal at the Foglight relay hole. For your OE foglights the relay is controlled by the DRL module. You will have to do some research on your rig, but it may all be there ready to use. Obvioulsy the switch and some stuff isn't present but alot seems to be.



This was neat, I would have never gone to look at that if your post wasn't started, Thanks. I guess I'm looking into puttin on some more lights. I'll post back when I get into it.



HTH

Wayne

 

[juicedcummins]

I haven't looked into too far except to find that it is the ground thats switching.

Thanks for trying to help me out and if I solve it I let you know.

My auto didn't have any harness at all at the bumper but it has the spot for the relay in the box.

This must be a tough one or one of the electrical brains would have replied also.

If I get the time I'll call Joel at bright-box,if he doesn't know it nobody does!

 

[redneckdr]

fog lights

all you have to do is use the switched ground for the brights for the ground on your relay. hook 12v+ to both the switch lug, and the bat+ lug on the relay, then a pigtail from the bright lights switched ground to the ground lug on the relay. the relay don't care whether the 12v+ is switched or the ground... ...

 

[juicedcummins]

thanks redneckdr; for the info and it will work. By the looks of it I have to use another relay to do what you just said. I also have it hooked up to a switch in the cab for constant use. This will take a couple of dioed's to stop the back-feed I think but I'll know once put to paper.

Thank You

 

[redneckdr]

diodes

i don't think with separate relays, you'll need diodes. the current can't bridge the switch in the relay?? you might want to put another switch in the 12v+ to the switched 12v+ lug, so that you can turn the fogs off, if you don't want them to come on every time with the high beams. i have my fogs wired completely independent of the headlights. that way, i can have them on with either the highs or the lows.

 

[wtrenholm]

Juicedcummins,



It appears that if you use the high beam circuit of the headlights themselves you may have the fog lights coming on with the DRLs also, as either the headlight switch or the DRL module can provide ground. It appears what will work is if you go off the hibeam indicator circuit, that's how they run the quad headlight relay with DRL, according to the diagrams.



Wayne

 

[juicedcummins]

I've also got a small problem with my bright-box and have had Joel on the phone and we were going to sort it out after a few tests on my end.

It is not the box in this case but a different aplication of the drls on this Can truck.

My drls are a certain% of high-beam and not low beam like the later trucks,or at least so I am told.

I am confident with Joel and believe he can solve the problem. Until then I'll have to sit back on this other fog-light question because I may be changing out the drl.

I also mentioned to him about this question on the fog lights and he said it would be a no -brainer for him once we solve the other prob.

Thanks for all you help guys I'll post the result after I fiqure it out with joel on this box.

 

[wtrenholm]

Juicedcummins,



If I remember right they pulse the circuit to control voltage which operates the high beams at something like 70-80% of intesity. This means the headlight switch gives unrestriced ground and the DRL module provides ground but basically put a resistance in series to lower the intensity.



I have no idea how the Brite Box is wired or what circuit requirments are, but possibly the high beam indicator circuit could be useful there also?



Wayne

 

[juicedcummins]

wtrenholm,you know this stuff dont you. .

I'm waiting for a fax from Joel at bright-box and should be in tuesday am.

I asked about the prob with my box and it has to do with the pulses that you mentioned above.

The fogs will have to wait till I get the brights staightend out.

Thanks for the help.