Throbbing lights

Discussion in 'General Chevy & GM Tech Questions' started by NEBRASKAHOE, Mar 29, 2009.


    NEBRASKAHOE New Member

    all my lights have a interior and exterior lights throb and i dont understand why. anyone have any idea???
  2. Jimmiee

    Jimmiee Epic Member 5+ Years 1000 Posts

    Any aftermarket accessories improperly installed? The first thing to do is clean your battery cables. Then if they still blink you need to have the charging system checked with a voltmeter. A bad alternator can emmit voltage spikes although the battery should absorb them.
  3. TrailLeadr

    TrailLeadr Epic Member 5+ Years 1000 Posts

    At the risk of not being serious, your subject line is killing me. lol


    What kind of vehicle, year, make and model please. We might be able to find something specific on it in the way of a tsb perhaps. but testing your battery, and alt would be a good place to start.
  4. Dr_Zero

    Dr_Zero Epic Member 5+ Years 500 Posts

    I had that same situation and cleaned the terminal and it didn't help mine turned out to be the alternator but it was intermittent, Easy enough to check just pull the alternator and take it to like Advance Auto or the likes and they can hook it up and test it for ya for free.
  5. KirkW

    KirkW Rockstar

    Do the lights pulse in time with the engine? I other words, if the engine speeds up, does the pulsing speed up as well?

    If so, then it sounds like your alternator has lost a diode (or two - there are six inside). That would produce a noticeable 'hump' in the output voltage. In fact, your voltmeter on the dash may show lower than normal voltage, especially with the headlights on - the voltage regulator can compensate a bit for the reduced voltage of a broken diode, but not at full load.

    If, instead, the lights are pulsing randomly, then it's likely a loose connection. Either something simple such as a battery or ground wire to the alternator, or something internal to the alternator (voltage regulator pack is loose or corroded.

    Try cleaning/reseating the connections to the alternator. If that doesn't work, then have the alternator tested.
  6. henrys021500hd

    henrys021500hd Rockstar

    This may not be the same but I recall reading somewhere that GM had a service bulletin about this and there was something they added onto a wire at the ALT to remove the spikes. My 02 has a flicker in the radio light but does not show up in the headlights, Henry.
  7. akairman

    akairman New Member

    a firends car did the same thing for a while. turns out there was a short in the little mirror light on the passenger side. i don't know the technical aspect of it, only when we disconnected it the problem went away. just my thoughts

    NEBRASKAHOE New Member

    Thanks guys.. I think its the altenator

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