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Hazard Switch

Discussion in 'Electronic Basics' started by [email protected], Jul 16, 2007.

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  1. Guest

    I am trying to figure out the electrical system on a 1997 GMC Sonoma
    pick-up truck. The problem I'm having is trying to understand the
    schematic diagrams. I have a set with bit more detail from Haynes.
    The diagrams depict the SUV which is similar. The area of interest is
    the Hazard/Turn/Stop functionality. The rear has one bulb per side
    with a filament for tail illumination and another filament for Stop/
    Turn. The front has one bulb per side with a filament for parking
    illumination and another filament for turning. Also, there is one
    sidemarker per side in front which integrates both parking and turning
    functions. I understand how the brake lights work with and without
    the turn signals on. I have also read about the strange way the turn
    signals work with the parking lights. Although, I think the schematic
    is incorrect. The real problem I can't figure out is when the hazard
    lights are on and I apply the brakes, all the lights that are flashing
    remain on (front, rear, and dash). This allows someone to know your
    braking when the hazard lights are on. But what makes it happen? I
    can't figure it out from the schematic. Is it me or the diagram? Can
    anybody figure it out? You can find my wiring diagrams at
    http://inboxjm.googlepages.com/home. Thanks!
     
  2. Lord Garth

    Lord Garth Guest


    In your diagram, the Stoplamp switch passes 'always Hot' power around
    the hazard flasher.

    If you were to disconnect the white wire, it would not stay on despite the
    brakes being applied.

    Find connector pin 17, the white wire and remove it. Apply 12 volts to
    the socket at the point and the lights will come on just as if you were
    braking.
     
  3. Guest


    I believe you misunderstood my question. I know that the stoplamps
    are fed always hot power through the Stoplamp Switch. However, when
    the switch is activated, that power is routed through the Turn/Hazard
    Switch Assembly, which determines which stoplamps can illuminate. The
    CHMSL is the exception, which can illuminate independent of the Turn/
    Hazard Switch. The diagram shows though that when the hazard switch
    is on, the stoplamp circuit is broken. But when I apply the brakes
    with the hazard lights on, the dash turn indicators cease to blink.
    Instead, they illuminate continuously until I release the brakes and
    they begin blinking once again. Thus, at the rear it would appear
    your stoplamps were on and at the front brighter parking lamps. Do
    you agree the diagram is incorrect? If so, how should the diagram
    appear to make me understand why "all" the hazard lamps freeze "on"
    with the brakes applied (i.e. what was Haynes' error?)? Also,
    wouldn't you agree that there are several more errors to the Turn/
    Hazard Switch Assembly? Look at the turn signal power input to the
    assembly. It doesn't get routed to all the right places.
     
  4. Lord Garth

    Lord Garth Guest

    I agree that the diagram appears in error. Looking at the turn flasher
    alone,
    there is no path to the turn signal lamps if the hazard switch is off.
    That's
    the purple wire on pin 16.
     
  5. Following wire #16 "south," it appears the position of the hazard contact
    is backwards, and that the path for the flasher signal is not completely
    drawn in. It should route to the NO contacts of the right turn relays as
    well as the left turn relays.

    |But when I apply the brakes
    |with the hazard lights on, the dash turn indicators cease to blink.
    |Instead, they illuminate continuously until I release the brakes and
    |they begin blinking once again.

    I agree that the diagram shows no path from the stoplamp switch to the
    lamps, so there is apparently another path line missing, and I would
    imagine that this path is to the far right NO hazard contact, and should
    contain a diode to prevent the flasher from operating the center brake
    lamp. Pure speculation, of course.
     
  6. Lord Garth

    Lord Garth Guest

    Is the diagram from a third party? Can you check one from the car maker?

    Otherwise, it's time to punt!
     
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