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Voltage reading while idling/cruising/WOT?

Discussion in 'Ford SVT Raptor General Discussions [GEN 1]' started by vegascarnut, Jun 1, 2020.

  1. vegascarnut

    vegascarnut Full Access Member

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    I've been doing some datalogging recently, and my voltage is reading between 12.8 and 13.4, averaging about 13.2. This seems low and I want to know what is normal? I can barely get 14 under WOT, but that's the only time I see something higher than low 13s. Curious to know what others are seeing. I am going to do some diagnostics with a multimeter later.

    Thanks,
    Sean
     
  2. IDI-Charlie

    IDI-Charlie Member

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    I'll see if I can do some looking with mine here this evening for you. Been wanting to see how my alternator stands anyway. How old is your battery?

    FWIW, my 7.3 charges at 13.8-14.3V with batteries that are on their way out. 13.8 is typically with high beams and A/C on.
     
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  3. vegascarnut

    vegascarnut Full Access Member

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    Thanks Charlie. My battery is fairly new. It's a Duralast Gold from Autozone. I have been told by a reputable person that they are crap, BUT I just want to rule anything else out before I start blaming the battery for the low voltage—if it's even low! My old battery was still humming along after 5.5 years, and nothing has changed. I only replaced it because it was so old. I just never measured the voltage with the old one.

    My main concern is that with the supercharger I want my fuel pump and injectors operating with as much juice as I can give them.
     
  4. vegascarnut

    vegascarnut Full Access Member

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    Update. Loaded an updated tune to correct some mild pinging and now my voltage is hovering close to 14 volts. Strange!
     
  5. vegascarnut

    vegascarnut Full Access Member

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    It gradually found its way back to 13.0 range, BUT I tested the voltage at the battery at idle: 13.5 solid. So the SCTx4 isn’t perfect.
     
  6. IDI-Charlie

    IDI-Charlie Member

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    Definitely sounds like it's reporting a bit off, may explain why it jumped after the tune flash. Unfortunately I didn't get a chance to test mine as things kept popping up - resulting in the truck staying in the garage until I get some pipe fab work finished.
     
  7. vegascarnut

    vegascarnut Full Access Member

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    I actually tested the voltage at the OBD port with a meter, and the OBD port is reading the correct voltage (matches alternator output). Something is wrong with the SCT device OR the cable. Working with SCT to get to the bottom of it.
     
  8. Traffic22

    Traffic22 Full Access Member

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    Not sure if this helps, but my UltraGauge, which is reading voltage (hardwired) from the OBD port, is consistently at 14.25, plus or minus less than .1 volt. (14.1-14.25 consistently.)
     
  9. vegascarnut

    vegascarnut Full Access Member

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    If I have no accessories on, no A/C, nothing, low 14s is my reading too, just not at the SCT device. Something is wrong with it—either the cable or the device itself. I need to get the voltage issue squared away so that I can trust the other readings. If it's wrong, who knows if the other readings are correct?
     
  10. Traffic22

    Traffic22 Full Access Member

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    That makes sense. You may be able to see if the SCT has an alternate voltage reading. I don't know the SCT, but the UltraGauge reads both voltage at the OBD, and the device itself, depending on the setting.
     
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