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Replaced battery and alternator but voltage meter keeps dropping.

Discussion in '1994-2004 V6 Mustang Tech' started by ItsReallyJ, Jul 29, 2019.

  1. ItsReallyJ

    ItsReallyJ New Member

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    So for the past month my car battery has been draining ive had a really old alternatot that blew, upon replacing the alternator the voltage regulator wiring crumbled, so for like a week i drove the car like that until it started to drain the battery.

    Got the wiring redone professionally it still drained the battery, got a new battery, seemed fine for one day, started to drain again, drove it home from work while it was on L, turned the car off, tried to start car and.... nothing.

    Can someone please help ive spent over $500 alone on just electrical issues alone, $300 on two alternators(shoudvle bought a 300 alternator but i was cheap, first one didnt fit and second one is 110 amps might not be strong enough), $200 someone to redo wiring, $70 for towing fees.

    I have a list of the posibilities

    -I think maybe the alternator isnt strong enough to keep charge with the batter its currently 110 amps instead of 130

    -Starter might be going out

    -parisitic drain somewhere

    -short somewhere

    -idk what, comment down below what you think
     
  2. Wulfe

    Wulfe New Member

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    You don't have an aftermarket radio or something like that installed do you? My ex fiance didn't wire hers right so it was always draining the battery.
     
  3. ItsReallyJ

    ItsReallyJ New Member

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    No its oem but when i look at the radio it does say cd error
     
  4. Pete fender

    Pete fender Pete Fender

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    Replace the short harness on the alternator. A burnt wire touching another is a fire ready to happen, plus a damaged wire can't allow charging current to flow as well.
    Never use any car with a damaged or burnt wire, just going over a bump could short something out.
    You really need to find the cause of the damage, before doing anything else.
    A short in any circuit may cause PCM problems.
    Stay away from alternators on eBay, they are mostly rebuilt in China.
     

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  5. ItsReallyJ

    ItsReallyJ New Member

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    The crazy thing is i bought the alternator from autozone and the first one from dbeletrical, but yeah if theres a short in the wiring i gotta find it asap. Ill update you guys once i find the issue.
     
  6. ItsReallyJ

    ItsReallyJ New Member

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    Upon watching a tutorial found out the issue it was fuse #6 cluster guage/pcm fuse it was pulling around 0.8, removed it shot down to zero, but the issue is, i cant get into gear because i removed the fuse. I dont want to have to take it to a shop again. Help please.
     
  7. Pete fender

    Pete fender Pete Fender

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    #6 may be part of the anti-theft system.
    Part of the PATS is in the cluster.
    The cluster has a blinking theft light in the gauge cluster, and draws current even when the key is out.
    You will always have a small voltage dr,just to keep radio presets, the anti-theft (PATS), and current to keep memory of driving habits store in the memory, and since PATS is anti-theft, removing the fuse may disable the shifter, as you need a signal to shift while stepping on the brake pedal.
    It's just like the battery i a PC, the PCM needs power to keep data in memory.
    The main CPU in OBDII PCM's is almost as powerful as a home PC or laptop, it can do many more things it is currently assigned to do.
    It needs constant current to hold volatile (Erasable) memory.
    I don't think that fuse is your problem.
    With everything turned off, and the car in a normal parking state, remove the ground terminal from the battery.
    Measure voltage between the battery post and terminal. There will always be a voltage drop, but it should be very low.
    Then, measure amperage draw at the same two points.
    It also should be low.
     
    Last edited: Jul 31, 2019
  8. Pete fender

    Pete fender Pete Fender

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    One more easy test.
    With engine running, measure voltage from the NEG Battery post to the alternator POS output.
    Then from Neg battery to POS battery.
    You the alternator should read the same as the battery.
    Subtracting battery to alternate4r, should be zero, or no more than .2 volts.
    If it is higher, clean the wire from the alternator to battery.
    You can also add a length of #8 wire from alternator output to battery, then it w2ilol read zero.
    The positive wires fro0m the alternator run all over the charging system and fuse-box supply.
    Bad connections add resistance, making alternator to battery resistance higher than the desired zero volts.
    Also check ground from engine to body, battery to engine block, and battery to body.
     
  9. Pete fender

    Pete fender Pete Fender

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  10. Pete fender

    Pete fender Pete Fender

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    Under hood fuses...
     

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