I'm having a problem on my car that I'd like to fix myself. I'm not a skilled electrician, nor an engineer, only someone with some mechanical skills. I apologize in advance, for any mistakes or misuse of electrical terms I may make. Please, bear with me and keep your answers as layman as possible.

On a DC12V automotive circuit wire, how can I block off any low voltage current coming through (say, anything under 9V), and still allow the normal 12V to go through, whenever the system on that circuit is activated? A wiring diagram would be immensely appreciated!

Thank you all for your time and knowledge!

  • are you saying that the high beam headlights are flickering when they are turned off?
    – jsotola
    Apr 16, 2022 at 1:44
  • Yes, jsotola, they flicker at all times, except when switch is on "driving lights" position. I apologize, I am looking for help with the actual problem!
    – IS250
    Apr 16, 2022 at 1:49
  • 1
    If the lights claim to be for your make model of car and they don’t work, you should take them back to where you bought them. Clearly they are faulty.
    – hacktastical
    Apr 16, 2022 at 1:56
  • there are modules that come preinstalled with the headlamps, I replaced both, but the same problem persists, Like I said, I've determined the problem to be a residual voltage coming through the high-beam wire on the circuit, pre-modules. I don't know the source of the residual signal. All I'm asking is how to block anything under, say, 9V on that wire
    – IS250
    Apr 16, 2022 at 1:57
  • I'm guessing the circuit doesn't use relays, instead has a solid state control module? Probably uses a low current to check for blown headlights or DRL compliance or something. You could use relays but you'd have to have a clean input source wire, which is a catch 22. You haven't provided a wiring diagram or even the make model year.
    – cde
    Apr 16, 2022 at 2:12

1 Answer 1


You can try this technique used when installing LED turn signal lamps. Wire a power resistor directly across your load. You can place the resistor at the end of a longer pigtail, and you may need to heatsink the resistor. But you can try a test setup with a 50 ohm resistor and without a heatsink. The resistor will bleed off any phantom voltage.

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