Time delay relay for aftermarket HID's & auto headlights.

Discussion in 'Lighting Discussion' started by 04SilveradoMykk, Dec 3, 2013.

  1. 04SilveradoMykk

    04SilveradoMykk Rockstar 100 Posts

    Hey guys,

    We all know that aftermarket HID's can't tolerate on/off/on in short periods of time. Exactly what happens at night when we turn the key on, start the engine and go.

    I'm sure there are several ways to skin a cat, but my idea included using a time delay relay on the switched source of the headlight relay. I'm sure most guys would disable/delete the auto headlights feature. I rather like it, just didn't want it taking out more HID ballasts.

    Found this wiring diagram online:


    As we can see, the BCM controls the ground of the headlight relay and is a pink/white wire. Pulled off the fuse/relay block cover, lifted up the block, poked around with a multimeter and found the lead that went to the headlight relay from inside the cab. I was shocked to see it was actually pink/white. Most of the time these wiring diagrams aren't even close.

    Installed the $5 time delay relay as per the schematic on the side. Paying close attention to polarity. Since the BCM sends a ground to the headlight relay, I used that as the time delay relay ground to start the "count" with the +12v on the nearest switched ignition source (a constant +12v would have been better)


    Set the dial to the desired time delay, I started around 10sec. Then realized half that much would work better seeing as the BCM kills the ground when the starter is going and then re-sends the ground starting the count over again.

    Give it a test, make sure everything works as planned. Lay the delay relay in the base of the fuse block, snap the block back down and clip the cover on. Alot like those snap together models as kids.



    Turn the key on, fire it up, by the time you put a seat belt on and put it in gear the lights are on and warming up.

    You could just as easily body ground the delay relay and hook the +12v to an ignition source while still controlling the BCM signal to the headlight relay. This would accomplish the same thing without resetting the count over when the starter engages. The benefit to using a constant +12v on the delay relay side is that the headlight switch will work without the key on, just with a delay.

  2. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    Great idea. I used those relays where I worked all the time.
  3. Flyinfool

    Flyinfool Rockstar 100 Posts

    Where did you get the $5 time delay relay from?
    This was one of the reasons that I do not yet have HID in my truck.
  4. Pikey

    Pikey Moderator Staff Member 5+ Years ROTM Winner 5000 Posts

    newark.com, digikey.com, automation direct. It looks like it is an omron H3y. I would love to know where he found it for $5. Cheapest I can find is $50. @04SilveradoMykk how is that catch can working? Where did you get it?
  5. Flyinfool

    Flyinfool Rockstar 100 Posts

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