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  1. #1

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

    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.

    Vortec 357ci Small Block Chevy: Big cam, high stall, long headers, rear gears. The typical formula.

  2. #2


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

    1995 Silverado 4x4
    6" BDS Suspension Lift-3" Body Lift-Add A Leaf in rear -Trailmaster SSV Shocks-Duel Steering Stabilizer Kit -AirAid Cold air intake-
    4.56 Gears with Detroit Auburn Locker-Pro-Comp Traction Bars with duel shocks-Aluminum Skid Plate Kit-38.5" x 16.5" Mickey Thompson Baja Claws-Constant Dropping fuel gauge

    2005 Yukon XL Jet Power Programmer, Bilstein Shocks, Bilstein rear springs, Helwig Anti-sway bars, EGR Window Visors, EGR Hood Shield, Denali Headlights, Headlight harness upgrade, GE NightHawk Bulbs, White Night Rear lighting system, Russell Braided SS brake lines, PowerStop Brake pads, PowerStop cross drilled and Slotted Rotors,
    2002 Silverado ext cab 2wd (Sold)
    2003 Yukon XL (Totaled)

  3. #3


    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.
    2011 Silverado, 1500, EX cab, 8' box, 4x4, 5.3l.

  4. #4

    Default,, 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. #5


    The time delay realys that we have been using on motorcycles for the HID are; $30
    or $15

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