Edgingage Posted February 21, 2021 Report Share Posted February 21, 2021 (edited) Hi folks, 2011 SEL here: We all know that, during daytime, with lights knob selected to automatic, the headlights AND signature/vertical/"fog" lights dim while driving. I've heard/read some comments stating the signature "fog" lights go to 50% and other comments stating they go to 70%, but it's not always clear to me if they're referring to luminosity or actual voltage. Does anyone know what's the actual voltage these lights dim at? In other words, and specifically, I would like to know what's the minimum operating voltage the signature/vertical/"fog" lights get when operating in dimmed mode. Your info is very welcome and greatly appreciated in advance. Edited February 28, 2021 by Edgingage Quote Link to comment Share on other sites More sharing options...
WWWPerfA_ZN0W Posted February 27, 2021 Report Share Posted February 27, 2021 headlights should not dim while driving. check to see what voltage is present at the connectors. if bulbs are old, they may be failing as well. do you have halogen or HID? Quote Link to comment Share on other sites More sharing options...
Edgingage Posted February 28, 2021 Author Report Share Posted February 28, 2021 (edited) Znow, thanks for your reply, I appreciate it. I realized my OP above was not clear; I just corrected the wording in my OP above. My question (as stated in the tittle) is regarding the power (voltage) getting to the vertical signature "fog" lights when the car is running during daytime as these lights function also as DRL then, but at reduced luminosity. Do you (or anyone else) know what voltage is powering the vertical signature "fog" lights when they're dimmed (while the car is running)? Luminosity is reduced; my understanding is that that's because the voltage getting to them is reduced. My question, what I'd like to know is: What's the voltage getting to the "fog" lights when the voltage is lowered during DRL and therefore their ("fog" lights) luminosity is diminished as a result of a lower voltage getting to them? Thanks in advance. Edited February 28, 2021 by Edgingage Quote Link to comment Share on other sites More sharing options...
enigma-2 Posted February 28, 2021 Report Share Posted February 28, 2021 Don't quote me on this, but I think I read somewhere long ago that they still operated at 100%, but at a reduced duty cycle. 70% on, 30% off or something like that. Controlled by a FET in the SJB. 1 Quote Link to comment Share on other sites More sharing options...
Edgingage Posted February 28, 2021 Author Report Share Posted February 28, 2021 Enigma, thank you very much for your reply. That's why I think I also read but I wasn't sure if that's regarding luminosity. So then I could interpret it as that the signature "fog" lights will operate dimmed at 12V x 70% = at 8.4V? Is my interpretation correct? Please let me know. Thanks in advance. Quote Link to comment Share on other sites More sharing options...
enigma-2 Posted March 2, 2021 Report Share Posted March 2, 2021 No, full 12.6 volts but at 70% duty cycle. (Full brightness for 70%, off for 30%. Thats how they run my DRL on my MKX only I think it's 50% for DRL). 1 Quote Link to comment Share on other sites More sharing options...
Edgingage Posted March 4, 2021 Author Report Share Posted March 4, 2021 On 3/1/2021 at 8:47 PM, enigma-2 said: ...Full brightness for 70%, off for 30%. Thats how they run my DRL on my MKX only I think it's 50% for DRL). Enigma, thank you VERY MUCH for you reply and explanation. You answered my main question; thanks again. If you wouldn't mind to please excuse my lack of electrical knowledge, could you please explain, spell for me what the above really mean?: "...off for 30%." I don't think they're ever off with the engine running... And to be honest, I don't even know/understand what "duty cycle" is (engine, alternator, ?). But again, you DID answer my main question (full 12.6V all the time) and I DO appreciate it. It's that "70% duty cycle" (of what?) plus "off 30%" (lights, which lights?) what leaves me in limbo; I'm puzzled (my lack of knowledge, I know). I'm sorry. But I now know what I wanted to know initially; thanks again. Quote Link to comment Share on other sites More sharing options...
enigma-2 Posted March 5, 2021 Report Share Posted March 5, 2021 On my MKX's DRL, they use a special transistor in the smart junction box (fuse panel) called a FET that turns the lights on and off really fast. At a 50% duty cycle, the lights are on 50% of the time, off 50% of the time. This results on having the headlights shine at a much lower light output. By using full voltage, the bulb reaches maximum light output, but for a shorter duration of time. Thus it appears dimmer. I believe that the same process is used in your case. When the lights are on, they are on at full voltage. Think of it as a light that's blinking very fast. With halagens, persistance of vision eliminates the flicker (your home lights flicker at 60 cycles per second. We don't see this because of persistence of vision. The flickering only becomes visible around 20 cycles per second.) With LEDs, I believe, but can't confirm, that they use a higher frequency to turn on and off the lights. As well as a longer duty cycle. Perhaps 70% on, 30% off to hide the flicker. It may be possible to see this by using your cell phone (the video camera can see the flickering). Maybe. 1 Quote Link to comment Share on other sites More sharing options...
Edgingage Posted March 7, 2021 Author Report Share Posted March 7, 2021 (edited) Enigma, I got it now! I really and greatly appreciate all your time sharing your knowledge and "spelling" it all out for me. Thanks a lot! Best regards! Edited March 7, 2021 by Edgingage Quote Link to comment Share on other sites More sharing options...
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