LED headlight / fog light interaction - looking for confirmation
Thread Starter
Racer
Joined: Dec 2017
Posts: 316
Likes: 63
From: Peoria IL
LED headlight / fog light interaction - looking for confirmation
Hi all,
I have LEDs in my fog lights (1996 CE LT1), and would like to go with LED headlights like the Osrams from Amazon I have seen people using. I have searched but I don't fully understand the interaction between the fog and headlight operation when LED headlights are installed with no added load resistance. I know the fogs are grounded through the headlights, but are the following statements correct when using LED headlights and no load resistors (keeping in mind that in my case the fogs are already LED)?
I know you can add the load resistors, but I may not have to. I only use the fog lights as DRLs. I don't drive the car at night that often, but when I do I don't care if the fog lights are on with the headlights or not. They don't do anything anyway. As long as I can use the headlights normally without the fogs, and can use the fogs with the parking lights only, I would be good to go.
Would anyone say the Hella conversion is a better solution? Any good links to those?
TIA C4 nation ....
I have LEDs in my fog lights (1996 CE LT1), and would like to go with LED headlights like the Osrams from Amazon I have seen people using. I have searched but I don't fully understand the interaction between the fog and headlight operation when LED headlights are installed with no added load resistance. I know the fogs are grounded through the headlights, but are the following statements correct when using LED headlights and no load resistors (keeping in mind that in my case the fogs are already LED)?
- If you turn on the fog lights with the headlights on, your high beams will come on regardless of whether you were on high beam or not?
- If you only have parking lights on and turn on the fog lights, the headlights do not come on?
- I can use headlights normally as long as fog lights are off?
I know you can add the load resistors, but I may not have to. I only use the fog lights as DRLs. I don't drive the car at night that often, but when I do I don't care if the fog lights are on with the headlights or not. They don't do anything anyway. As long as I can use the headlights normally without the fogs, and can use the fogs with the parking lights only, I would be good to go.
Would anyone say the Hella conversion is a better solution? Any good links to those?
TIA C4 nation ....
Last edited by turtle96; Nov 20, 2019 at 02:45 PM.
Team Owner
Joined: Dec 2003
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From: When all is said and done... there is a hell of a lot more said than done. Riverside,Texas
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Not sure about a '96, but I'm pretty sure item 1 is wrong, I think the fog lights would kill the high beams. If you consider the purpose of fog lights, the idea is to throw light low on the road, high beams would reflect off the fog and create glare.
Pro
Joined: Oct 2012
Posts: 580
Likes: 121
From: Grapevine TX
I have a 96 and can confirm that points 1 and 3 are correct. I've never tried what you suggest in point #2, hopefully someone will pitch in who's tried it.
There is a workaround for the issues, do a search for user Circuit Doctor. Not sure if that's one word or two. He came up with a method to connect a small incandescent turn signal type bulb into the headlight wiring to provide the circuitry required by the fogs to make everything work correctly. I can confirm his method does work.
There is a workaround for the issues, do a search for user Circuit Doctor. Not sure if that's one word or two. He came up with a method to connect a small incandescent turn signal type bulb into the headlight wiring to provide the circuitry required by the fogs to make everything work correctly. I can confirm his method does work.
Burning Brakes
Joined: Jan 2019
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From: Park City, TN
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I have turned my fogs on and off with the headlights on and it does nothing to hi/low beam.
Yes, #2 is correct. I run with parking and fog lights on and headlamps off.
Thread Starter
Racer
Joined: Dec 2017
Posts: 316
Likes: 63
From: Peoria IL
Thread Starter
Racer
Joined: Dec 2017
Posts: 316
Likes: 63
From: Peoria IL
I have a 96 and do not agree on #1. It doesn't make sense since the proper thing to do in fog is to always use low beams, not high.
I have turned my fogs on and off with the headlights on and it does nothing to hi/low beam.
Yes, #2 is correct. I run with parking and fog lights on and headlamps off.
I have turned my fogs on and off with the headlights on and it does nothing to hi/low beam.
Yes, #2 is correct. I run with parking and fog lights on and headlamps off.
When you replace the stock headlights with LEDs you significantly reduce the resistance in the system, so the system's operation changes. What I'd like to know if the system functions like I outlined in my 3 points above when LED headlights are installed with no load resistors or circuit doctor fix (this last point is what I failed to make clear in my original post). I am not asking about the factory setup.
Hope this helps people understand my question. Thanks.
Last edited by turtle96; Nov 20, 2019 at 02:48 PM.
Race Director
Joined: Mar 1999
Posts: 12,597
Likes: 237
From: Bartlett Illinois
On my 1990, the fog lights get +12v but are controlled by a relay that is grounded through the Highbeam. so When I turn on the High beam, the relay has 12 on both sides of its control coil and turns off the Fog lights. I added another relay to guaranty the lights will work as designed with LED or Halogens..
One added relay:
Find Fog Light relay
Cut Lt Grn (Or extract pin)
Power side of Lt Grn to Pin 86 of New Relay
Pin 85 and Pin 30 of New Relay to Ground (New Wire)
fog light side of LT Grn to New Relay 87a.
If you want DRL on Fog Lights.. This requires its own relay
DRL Fog lights only (always on)
Remove PPL wire from factory fog relay (87)
86 - coil power - power source when parking lights are on.
85 - coil ground - ground
30 - com switch - PPL wire from OEM Fog relay
87 - NO contact - connect to (87) on Fog relay
87a - NC contact - power source to handle fog lights for DRL
One added relay:
Find Fog Light relay
Cut Lt Grn (Or extract pin)
Power side of Lt Grn to Pin 86 of New Relay
Pin 85 and Pin 30 of New Relay to Ground (New Wire)
fog light side of LT Grn to New Relay 87a.
If you want DRL on Fog Lights.. This requires its own relay
DRL Fog lights only (always on)
Remove PPL wire from factory fog relay (87)
86 - coil power - power source when parking lights are on.
85 - coil ground - ground
30 - com switch - PPL wire from OEM Fog relay
87 - NO contact - connect to (87) on Fog relay
87a - NC contact - power source to handle fog lights for DRL
Last edited by -=Jeff=-; Nov 21, 2019 at 11:31 AM.
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Burning Brakes
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From: Park City, TN
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Pro
Joined: Oct 2012
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From: Grapevine TX
Sorry guys, let me (hopefully) clarify my question. I understand that the design intent of the stock system is to shut off the fog lights when you turn on high beams. It does this by grounding the fog lights through the high beams (as I understand it).
When you replace the stock headlights with LEDs you significantly reduce the resistance in the system, so the system's operation changes. What I'd like to know if the system functions like I outlined in my 3 points above when LED headlights are installed with no load resistors or circuit doctor fix (this last point is what I failed to make clear in my original post). I am not asking about the factory setup.
Hope this helps people understand my question. Thanks.
When you replace the stock headlights with LEDs you significantly reduce the resistance in the system, so the system's operation changes. What I'd like to know if the system functions like I outlined in my 3 points above when LED headlights are installed with no load resistors or circuit doctor fix (this last point is what I failed to make clear in my original post). I am not asking about the factory setup.
Hope this helps people understand my question. Thanks.
And I'll reiterate my earlier reply. I have the Truk-Lite LED headlights in my 96. When I first installed them I had no resistors and the Circuit Doctor mod hadn't been posted yet. In that configuration, when I turned on the fogs the high beams would also come on. It didn't matter if I pulled the turn signal lever to try to switch between high and low beams, the high beams stayed on. If I turned the fogs off then the headlights reacted normally, switching between high and low beams with the pull of the lever.
