Bad alternator but its new ?

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by Roman78, Aug 14, 2022.

  1. Roman78

    Roman78 Light Load Member

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    have cummin isx i have batteries icon on dashboard. I changed batteries same problem my powerdrive 3000 kw innovator can only run a laptop lol. If i turn on the printer for example it would restart and go crazy it would run the printer but every time i print a page inventor restarrt it self. I run a test using the power drive app. Batteries result came good. But alternator result came bad. So i went and bought me new alternator after 2 hours under the sun at the truck stop i managed to install the new alternator. Installed the belt and now its doing the same thing. Poor power with red battery icon on dashboard battery .
     
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  3. skallagrime

    skallagrime Road Train Member

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    Run your rippums to 1400, see if your voltage spikes.

    But yes, entirely possible the brand new alternator is bad

    Might be lucky and you just didnt tighten the pully bolt hard enough/not tension the alternator
     
  4. AModelCat

    AModelCat Road Train Member

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    Get a digital multimeter and check voltage between alternator positive and the alternator case. If its 14-ish, check the batteries. If batteries are not within about 0.5 volts of the 14-ish volts the alternator should be producing then you have a wiring issue somewhere in the charging circuit.
     
    Last edited: Aug 14, 2022
    baha Thanks this.
  5. Roman78

    Roman78 Light Load Member

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    New alternator test at 12.
     
  6. kranky1

    kranky1 Road Train Member

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    It should be 14.5
     
  7. AModelCat

    AModelCat Road Train Member

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    Does it have an external regulator?
     
  8. Roman78

    Roman78 Light Load Member

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    No. I get this code sometimes.
    mid 144 psid 230 fmi 5
     
  9. Six9GS

    Six9GS Road Train Member

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    It is entirely possible to have a 'brand new' alternator that is bad out of the box. It's not common, but does happen. It has happened to me twice (4 wheeler) that I can remember over the years. If there is some way to get the alternator tested, that would be my next step. I can't speak to what voltage levels should be coming out of the alternator in a semi. For an older 4 wheeler, anywhere between 13.8 volts to 14.2 volts is the usual, depending upon brand and model. These new cars have alot more computer control on all the systems and unsure how that effects things like alternator voltage.
     
  10. AModelCat

    AModelCat Road Train Member

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    Does it need to be field flashed?
     
  11. kranky1

    kranky1 Road Train Member

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    Probably should be bic flicked in a field. That should take care of any computer related problems.
     
    AModelCat Thanks this.
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