Twinkling lights
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HT4100 4.1, 4.5, 4.9 Discussion, Twinkling lights in Cadillac Engine Technical Discussion; The beast I call Frank is still alive. Despite my worry the tranny was dead before and some other issues ...
  1. #1
    MrDobin is offline Cadillac Owners Fanatic
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    Twinkling lights

    The beast I call Frank is still alive. Despite my worry the tranny was dead before and some other issues which I ironed out and repaired.

    I now have however a wacky electrical issue. For the past few weeks I have noticed a twinkling effect going on with my interior lights and headlights. There is no correlation to any specific speed or gear, its constant. On a few occasions the twinkling stops while I am braked at a stop or when parked. However for the most part whether accelerating or decelerating, the lights all twinkle. I took it in for a charge test and its pumping out a solid 15v from what I saw on the tester at the shop. So all that tells me is I have a short somewhere or something.
    The "twinkle" by the way is not an off and on sort of effect. The lights simply waver between two points of intensity as if the power was being turned up and down in short intervals. This twinkle also seems to increase in speed when at high RPMs. I don't think the new alternator is the culprit as its new, but maybe I drew the short straw. Unsure if this is important but Pretty sure my Air Vac pump is on the fritz so it might be causing issues?. Took the belt off the pump and the knock/pump sound i was having went awake but the lights seems to only mildly improve as a result.

    Throw any ideas or theories you guys have out. I rather not get a new alt, but if need be I guess so.

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  3. #2
    carnut is offline Cadillac Owners Master
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    Re: Twinkling lights

    15 volts is .7 of a volt too high. 14.3 to maybe 14.5 is max. I think you're seeing the internal voltage regulator attempting to lower the voltage. 15 volts will burn out headlights, dome lights and damage the computer. This car was famous for a slipping smog pump belt which then causes the alternator to slip on its belt at higher RPMs. Look closely to how the alt belt only wraps around the water pump pulley, if the smog belt is loose then that will allow the water pump pulley to slip. Rather a hard belt to tighten, you must get under the car to loosen the smog pump then pry the pump away from the block. Quickest way to confirm a slipping belt is to try to rotate, by hand, the alternator pulley in an opposite rotation ( ENGINE OFF ). If you can move it at all, the smog belt is either worn out or too loose.

  4. #3
    MrDobin is offline Cadillac Owners Fanatic
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    Re: Twinkling lights

    Yea. Voltage is steady below 15.

    Unhooked the air pump pulley belt and sprayed it down to stop any slippage. Connected, tighten, and upon starting the car found what very likely is the issue. The pump pulley is wiggling like mad, no doubt reason for some issues. Will start looking for one ASAP. My question now is whats the danger of unhooking the pulley should it fail? And can I fit a different style of pump on assuming the pulley fits the belt style?.

  5. #4
    carnut is offline Cadillac Owners Master
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    Re: Twinkling lights

    I'm confused??? You first say its 15 volts then you says its steady below 15. Which is it? Taking off the belt to the vacuum pump will affect power brake operation making the car unsafe to drive. How could you have looked under the hood before and not noticed the bent pulley? Spraying belts is never a repair, only a diagnostic tool to confirm a faulty belt. Is the smog pump belt loose or not. You say removing the belt made the noise go awake???? Please be more clear on your issue. We are here to help not try to figure out what you are trying to say

  6. #5
    MrDobin is offline Cadillac Owners Fanatic
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    Re: Twinkling lights

    My apologies. Spaz mode when it comes to new issues coming up. Shocking I haven't developed some sort of psychosis given this car ha.

    I should have sprayed prior to wondering now that I think of it. The pulley has wiggled a small amount forever, spraying it likely confirmed and increased what was already there. Thus, I no doubt need a new pulley. Just am hoping that's the reason for the wacky lights. Somewhat supporting the pulley idea is when I am idling or stopped fully in drive, the lights smooth out as does the wiggling pulley.

    Will order up and update, thoroughly

    Thanks for the input carnut, always helpful.

  7. #6
    carnut is offline Cadillac Owners Master
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    Re: Twinkling lights

    A bent vacuum pump pulley will not affect " twinkling" lights. A loose smog belt will, a faulty voltage regulator will.

  8. #7
    MrDobin is offline Cadillac Owners Fanatic
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    Re: Twinkling lights

    Carnut I think you hit it on the head.

    My idiot self miss took words. Look at the belt for the vac pump NOT the air smog, bingo. Its also where the thump I have been getting is coming from, I think.

    Going to look into it more tomorrow.

  9. #8
    MrDobin is offline Cadillac Owners Fanatic
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    Re: Twinkling lights

    Its a cheap part, and I have a hunch I burnt it out when I put my old battery from my car, to my mom's escalade, then back that I damaged the regulator. The noises are all the same as before, no problems have developed, but given the timing now that I have looked, and thought, regulator seems right.

    If I pick one up is there anything needed to install beyond the part itself?. I see no point in buying an entirely new alt.

    Thanks again

  10. #9
    carnut is offline Cadillac Owners Master
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    Re: Twinkling lights

    You do know the regulator is inside the alternator, correct?

  11. #10
    MrDobin is offline Cadillac Owners Fanatic
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    Re: Twinkling lights

    Lol

    Ya. I'm just not able to see if the regulator is linked to anything which will also need replacing. I took my other two alts apart so its not alien to me

  12. #11
    MrDobin is offline Cadillac Owners Fanatic
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    Re: Twinkling lights

    Too further support the regulator as problem I did a mickey mouse sort of test to it. When my last alt blew its regulator I turned on all the gizmos in the car to hold down the output. So tonight after work I put the car in drive, stopped it fully, and held all the window switches up at once. Ta da, light flicker gone, until I hit the gas.

    Only thing now that puzzles me is how did I damages the regulator, unless when the fried battery I had was put back in my car burning hot after being in my moms much larger, escalade, hurt it. I would never have expected a regulator to have fluctuation if damaged, unless that in itself is a sign its not doing its job. I dont know.

  13. #12
    MrDobin is offline Cadillac Owners Fanatic
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    Re: Twinkling lights

    The conclusion of the long annoying alternator has come at last. I finally got around to getting a regulator from NAPA. Was 15 bucks and plenty worth the chance it may fix the issue rather than a new alt. I went to replace it today and to my amusing yet annoyed surprise, i found the issue. The alt i had bought was poorly assembled and two out of three of the regulator screws were at less than half driven in. I tighten them up. Then saw there was residue or grease on the shaft in the alt and wiped it. Not shockingly the gunk was on ONE spot of the shaft in the generator and so made sense why I had a "twinkling". Reinstalled the alt and started Frank(name of the car) and runs like a champ.

    Here is the amusing part though, and maybe someone can give insight to what would be the sound. I let it idle for a minute or so and the previous knock from which i was sure was the air pump, is gone. I am not sure outside of the distributor and a piston what would knock but maybe the gap in the alternator rotation was making a loss of current somewhere. No idea. But, all is well now.

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