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  • pulsing lights

    have a 2005 reg cab silverado 1500. the lights started pulsing at night. it is almost like the truck has a heart beat. have changed the battery and the altenator says it's charging properly. any ideas guys?

  • #2
    Re: pulsing lights

    Originally posted by evanmcleod88 View Post
    have a 2005 reg cab silverado 1500. the lights started pulsing at night. it is almost like the truck has a heart beat. have changed the battery and the altenator says it's charging properly. any ideas guys?
    My 2001 silverado does the same thing, well, every now and then the headlights will dim pretty good on a dark road. Doesnt seem to be related to the A/C kicking on or anything, and like you my battery and altenator are both good. I have no idea. It does seem like a heartbeat....or that may be wishful thinking

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    • #3
      Re: pulsing lights

      all my lights do it even interior lights.

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      • #4
        Re: pulsing lights

        Originally posted by evanmcleod88 View Post
        all my lights do it even interior lights.
        oh now thats weird. Have to research that a little

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        • #5
          Re: pulsing lights

          I have a friend with an 05 S10 that does the same thing and it drives me crazy to ride in it! All the interior lights and headlights pulse. I figured it had to be charging system related, but he's never tried to fix it.

          Has anyone tried replacing the alternator? This has to be a fairly simple fix.


          '96 Tahoe...5.7 Vortec...4wd...~205,000...Stock

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          • #6
            Re: pulsing lights

            my 94 does it.. i was told my alternator was putting out to much, i havent got a new one to see if it fixed the problem yet tho

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            • #7
              Re: pulsing lights

              ya altenator is a little pricey to just be changing out.. how i miss warranty!

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              • #8
                Re: pulsing lights

                It's the voltage regulator in the Alt.
                2016 Carlisle All Truck Nats info..
                http://www.fullsizechevy.com/forum/o...g-5th-7th.html

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                • #9
                  Re: pulsing lights

                  Originally posted by CKTA View Post
                  It's the voltage regulator in the Alt.
                  So you've experienced this and you're sure?


                  '96 Tahoe...5.7 Vortec...4wd...~205,000...Stock

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                  • #10
                    Re: pulsing lights

                    Could be BCM

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                    • #11
                      Re: pulsing lights

                      If you have a voltmeter, put it on the battery with the truck running. It should be no more than 14.4v and no lower than 13.5ish. Your pulsating lights could be the voltage regulator "bouncing" up and down, or running too low and bouncing up and down. Also check you battery connections and make sure you don't have a deteriorated connection. If you don't have a voltmeter, go to Autozone or a parts store that will come out and test your battery in the vehicle. Their tester will have a voltmeter as part of the test.
                      1998 GMC Sierra SLE 1/2 ton 2WD 305 Vortec
                      -Gibson Stainless Cat Back Swept Side
                      -255/70 BFG Radial T/A on SS 15's


                      :nutkick:

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                      • #12
                        Re: pulsing lights

                        You have your sub's turned up too loud. Either tone down the boom boom or have a huge, neon painted, capacitor put on the positive feed. You could also try putting some "optima" stickers on the back window. lol! kidding!

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                        • #13
                          Re: pulsing lights

                          I know this is an old post but maybe someone can shed some light. I have a 1989 3500 crew cab with a 350/tbi. My headlights started pulsing ( not all the time )
                          and when they do it the alt gauge jumps back and forth along with the lights. I was guessing voltage regulator but welcome any input.

                          thanks

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                          • #14
                            Re: pulsing lights

                            A lot of these phantom electrical problems can be related to bad connections. Connect a volt meter between the alternator output and the POSITIVE battery connection. There should be a low or no reading, if you get a reading at or above 12-13 volts there is probably a bad connection somewhere. Do the same thing on the ground side between the alternator case and the negative battery terminal. Also depending on where your negative cable connects, there can be a bad ground between engine and chassis, chassis and body etc. Basically the engine sits on rubber mounts the body sits on rubber mounts so all these things need to have proper ground connections. Again any significant reading on any of the ground connections probably indicates a corroded ground connection. Personally I would check all these things before throwing parts at it.

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                            • #15
                              Re: pulsing lights

                              x2 check grounds, but I'd say most likely you have at least one burned up diode in your alternator's rectifier bridge (possibly more). Alternator then only works 1/3 or 2/3 phases, so it still charges battery, but the current dips and voltage fluctuates between 12.5-14 at whatever frequency the alternator is putting out (more noticeable at low engine rpm).

                              I noticed this on my 4.3 blazer at stop lights and just in general after some big stereo abuse (even when stereo was off). Upgraded to ad244 alternator =).

                              You can maybe replace the rectifier yourself depending on comfort level. http://springhillautoelectric.com/ is the only source I've found...

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