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Hot Rods 3 wire alt wiring???

Discussion in 'The Hokey Ass Message Board' started by ALLDONE, Feb 13, 2026 at 7:55 PM.

  1. ALLDONE
    Joined: May 16, 2023
    Posts: 4,039

    ALLDONE
    Member

    Problem... my ford f100 has a parasitic battery drain....enough that it pulls the battery down to 6 volts over night...so I've been going through the wiring....looking at the alt I noticed that the power wire was going to the number 1 spade... and it should be going #2 and @ 2 spade was going to the loom into the dash,,,,, my guess is it the gen light???.... so trying to think back.... I remember taking a piece of wire wrapping it around a Phillips and making a little coil and plugging it in to both spades,,,, seem like it worked well ???? So I un hook the plug. and just plugged the power wire to #2... started it up 14.2 volts... and shuts off with the key.... seems to me I remember the #1 spade doesn't even have to be hooked up.. but if you use it it either has to be hooked up to the gen light or acc power or the truck won't shut off.... not sure that the alt wired wrong was my problem.... my gauge doesn't show an amp draw... and waiting till tomorrow will tell....my idea is that hooked wrong keeps the alt energized ??? what say you... is it ok to not use #1 spade
     
    chryslerfan55 likes this.
  2. RICH B
    Joined: Feb 7, 2007
    Posts: 6,064

    RICH B
    ALLIANCE MEMBER

    Usually jump battery terminal to #2 and then #1 is powered by the ign either thru the indicator light or diode if using a voltmeter.

    Don't think it will charge if #1 isn't used.
     
    chryslerfan55 likes this.
  3. Kosmos55
    Joined: Feb 23, 2022
    Posts: 165

    Kosmos55
    ALLIANCE MEMBER

  4. ALLDONE
    Joined: May 16, 2023
    Posts: 4,039

    ALLDONE
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    its charging 14.2 without it...
     
  5. 29Sleeper
    Joined: Oct 25, 2023
    Posts: 587

    29Sleeper
    Member
    from SoCal

  6. ALLDONE
    Joined: May 16, 2023
    Posts: 4,039

    ALLDONE
    Member

    the question I still have is if the battery wire is hooked to #1 instead of two... would it keep the sensor energized and drain the battery?
     
  7. ALLDONE
    Joined: May 16, 2023
    Posts: 4,039

    ALLDONE
    Member

    I don't understand??? if it was shorted would it still charge 14.2 volt in the battery when running???
     
  8. ALLDONE
    Joined: May 16, 2023
    Posts: 4,039

    ALLDONE
    Member

    heres what i think, and would be easy to test... turn the key to on... but not start.... the #1 would light the test light... as soon as the motor is started.... the light would go off.....with the wires hooked backwards the sensor would be hot all the time,,,,, correct???
     
  9. swade41
    Joined: Apr 6, 2004
    Posts: 14,576

    swade41
    Member
    from Buffalo,NY

    I reversed mine in haste and it drained the battery, took a bit to figure out what was going on but once on the right terminals all was good

    20240520_164732.jpg
     
    twenty8 likes this.
  10. RICH B
    Joined: Feb 7, 2007
    Posts: 6,064

    RICH B
    ALLIANCE MEMBER

    Battery hooked to #1 would be a draw.

    Wired correctly and you turn the key; but didn't start it, there would be power at #1. Once started, there would still be power at #1. That's why you need a light bulb or diode in line*; otherwise it back feeds the ignition and the engine won't shut off.

    * Or some other way to isolate #1; such as wiring it to the accessory terminal on the ignition switch.
     
    rusty valley likes this.
  11. rusty valley
    Joined: Oct 25, 2014
    Posts: 4,392

    rusty valley
    Member

    A diode is a one way valve. So, (if wired correctly). it can charge while running, but will discharge while you sleep if its bad
     
    Last edited: Feb 14, 2026 at 10:31 AM
  12. ALLDONE
    Joined: May 16, 2023
    Posts: 4,039

    ALLDONE
    Member

    I think thats close...but will check today...and I think it'll work fine with out the #1 hooked up...

    but I will do a test today...., if the battery didn't die over night... I think the # 2 has battery sleep volts... same as # 1...which is 12.2 volts or less.... when you spin the alternator the volts go to 14.2... when that happens it shut power to # 1.... and if the alternator starts going bad and puts out less than 12.2 while spinning... #1 lights up.... the only thing I see happening if you don't hook up the #1 wire is without a volt meter you would not know that the alternator quit charging...
     
  13. ALLDONE
    Joined: May 16, 2023
    Posts: 4,039

    ALLDONE
    Member

    Well... good news... sat over night and still at 12.2v..dark out so didn't do the alternator test... but I think alls good... took a minute to find the battery draw..... but found it...
     

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