voltage drops when car in drive
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Northstar Engines and System Technical Discussion Discussion, voltage drops when car in drive in Cadillac Engine Technical Discussion; i have a 1995 cadillac eldorado with the northstar motor. When the car is in park i have about 12 ...
  1. #1
    louie k is offline Cadillac Owners Member
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    voltage drops when car in drive

    i have a 1995 cadillac eldorado with the northstar motor. When the car is in park i have about 12 volts, when i put the car in drive the volts drop rapidly down to about 8. When i put the car back in park the volts go right back up to 12. The belts are working. does anyone know what might cause this?

    thnx in advance
    louie

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: voltage drops when car in drive

    How are you measuring voltage? I wouldn't trust any gauges... Use a volt meter at the battery terminals and confirm those readings. 12 volts is very low, you should be seeing around 14 at idle.

  4. #3
    1993 eldorado green1's Avatar
    1993 eldorado green1 is offline Cadillac Owners Fanatic
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    Re: voltage drops when car in drive

    yep, what eldorado said. 14 at idle and it should stay about the same in drive although it may drop a little if your running accessories and such.

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    dkozloski's Avatar
    dkozloski is offline Cadillac Owners 10000+ Posts
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    Re: voltage drops when car in drive

    If the lights are flaring from orange to bright with engine speed, the battery is shot.

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    Zorb750 is offline Cadillac Owners Connoisseur
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    Re: voltage drops when car in drive

    Or your voltage regulator is bad.

    Same thing if you hit the brake and the headlights momentarily dim a bit and come back (less than a second).

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    louie k is offline Cadillac Owners Member
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    Re: voltage drops when car in drive

    it says how many volts for the battery in the dash. when i start the car and let it idle it says 12.5 or around there, then when i put the car in drive it drops down to 8 and says battery volts low, i have air conditioning off, radio off, lights off in car. i checked the battery with a tester when the car was off and it said 2/3 full. i havent checked it when the car was in drive though.
    When i hit the brake my headlights do dim of less than a sec and then come back

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    1993 eldorado green1's Avatar
    1993 eldorado green1 is offline Cadillac Owners Fanatic
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    Re: voltage drops when car in drive

    Quote Originally Posted by louie k
    it says how many volts for the battery in the dash. when i start the car and let it idle it says 12.5 or around there, then when i put the car in drive it drops down to 8 and says battery volts low, i have air conditioning off, radio off, lights off in car. i checked the battery with a tester when the car was off and it said 2/3 full. i havent checked it when the car was in drive though.
    When i hit the brake my headlights do dim of less than a sec and then come back

    sound to me like its time for a new alternator man.. there not too bad to change

  9. #8
    zonie77 is offline Cadillac Owners Connoisseur
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    Re: voltage drops when car in drive

    There's a part in the alternator called a rectifier. If one of the diodes in the rectifier goes it acts like that.

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    blunted is offline Cadillac Owners Enthusiast
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    Re: voltage drops when car in drive

    Not to thread jack.. but you guys are getting me paranoid. Mines never at 14.. i get 13.5 max. I'm running at 7" Head Unit and 3 12"subs 1000W Amp, however I dont constantly have them blasting. Everything seem ok there? I got a Yellow Top as well.

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: voltage drops when car in drive

    Again, check at the battery with a meter to confirm. It could be a simple wiring problem, or nothing to worry about.

    As an example, my ECM was showing 13.5 volts running, but I measured at the battery to be 14.5 volts. Now I know it's not the alternator, so I stopped worrying about it. A 1 volt drop is more than I'd like to see, but short of ripping out wires and buying all new connectors and smearing everything with new dielectric grease, there's nothing I can do.

  12. #11
    Polski Polak's Avatar
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    Re: voltage drops when car in drive

    how do u know whether its the alternator or the battery, my headlights dim when I roll up my window should i look into a battery or alternator??? thanks in advance!!!

  13. #12
    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: voltage drops when car in drive

    You can have your battery tested at Autozone or similar. The alternator can be tested in the car at the same.

  14. #13
    acklac7 is offline Cadillac Owners Fanatic
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    Re: voltage drops when car in drive

    Quote Originally Posted by Zorb750
    Or your voltage regulator is bad.

    Same thing if you hit the brake and the headlights momentarily dim a bit and come back (less than a second).

    Where is the voltage regulator located at ? ....For the past few years my headlights have dimmed when I apply the brakes....The engine will also make a slight noise at the same time....A buddy of mine said this was indicitave of the engine "looping" or something like that...BTW my volts rarely read over 13.5...when I have accessories running the voltage is in the mid-high 12's...Which is way to low I believe...I'd love to fix the problem...If it's something cheap and simple

  15. #14
    caddyfanatic2 is offline Cadillac Owners Member
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    Re: voltage drops when car in drive

    My headlights on my mazda 626 dimmed when i hit the brakes too. I figured it was something to do with the circuit that did the bulb check. But I've been noticing it on my Cadillac too. What could that be? Dont all cars do that?

  16. #15
    thu's Avatar
    thu
    thu is offline Cadillac Owners Connoisseur
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    Re: voltage drops when car in drive

    You can also just take your car down to Sears Automotive. They'll test the entire electrical system for you. Some stores to it for free; others charge a tiny fee. Many will waive the fee if you buy a batt, alternator, etc.

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