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Amp Light On/dead Battery

Discussion in 'Jeep Truck and FC Tech' started by jeepstar, Oct 3, 2023.

  1. Oct 3, 2023
    jeepstar

    jeepstar Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Sheboygan
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    1959 FC-150, f134.

    so, when it rains, it pours. last week I thought the carb needed a rebuild. then it fired right up after sitting overnight, so I changed the fuel filter and its been running fine for the last 2 weeks.

    this entire summer the amp light has been on, but no issues starting the jeep ever, at any time, so i figure its just turned into a dummy light at this point.
    80 mile round trips, no issues. on Sunday the wife and I took a ride to a little town to see a car show, about 35 miles away. we get there, are the only ones that showed up, so we won first place. jeep starts fine. start heading home, make a few stops on the way home, then on the last stop, I go to turn the key, the battery is dead. I had to knock on a guys door, ask him to tow start me, so I can drive home.

    we start my jeep, wife jumps in, and off we go. park it in the garage. next day after work, I go to start it and nothing. the battery is dead.

    while poking around under the doghouse I noticed my fan belt was in dire need of replacement, so I bought a new one.
    the belt never squealed, is it possible it was slipping/not turning the generator without squealing?

    upload_2023-10-3_6-40-27.png

    I know nothing about generators. how do I know if it is working?
    I dropped my generator off at an electrical motor place, they said they will try to test it for me, see if its good or bad but they weren't sure if they could do it.
    If they cant test it, I think I will put in a 1 wire GM alternator. another thought is my voltage regulator. that may be bad.

    what else can I check?
     
  2. Oct 3, 2023
    Howard Eisenhauer

    Howard Eisenhauer Administrator Staff Member

    Tantallon, Nova...
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    With the engine running at anything over a fast idle voltage at the battery should be ~13.5 to 14.5 volts.

    If it's @ ~ 12.something volts that's an issue- could be the generator or the regulator.

    While the engine is running , again above fast idle, take a clip lead & , while measuring the voltage at the battery, connect the genny "Field" terminal ( the smaller stud closer to the engine block) to ground for 4-5 seconds while observing the voltage- if it shoots up to a high level the genny is good & it's the regulator that's bad. If it doesn't it's a bad generator.
     
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  3. Oct 3, 2023
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
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    A simply loose fan belt could well have been the root cause of the non-charging, or long term partial charging. Eventually you had enough power to run the ignition, but not enough to crank the starter. The idiot light was trying to tell you.

    An alternator swap seems unnecessary to me, and would do nothing to cure basic upkeep issues like a worn out belt. In the time these Jeeps were built, frequent routine maintenance was the norm - 60 years later it should be even more so.

    I certainly would not trust a shop that doesn't know how to test a generator. Jeezum. Inspect/clean the brushes and commutator. Put 12 volts to it, it should motor itself.

    Get your FSM, and read up on "polarizing" your generator and regulator. Easy but important, especially after re-installation.
     
    Last edited: Oct 3, 2023
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  4. Oct 3, 2023
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Pullman, WA
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    Check the battery too. if it ran after jump starting, the charging system is at least doing something. Charge it up and take the battery to an auto parts store and have them load lest it.

    They can die surprisingly quickly when they go.
     
  5. Oct 3, 2023
    jeepermc

    jeepermc Active Member

    Western WA
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    My amp light comes on in the CJ6 when the generator isn't charging. Mine is a stuck brush I think as it's random, and a sharp whack with a hammer will fix it. lol
     
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  6. Oct 3, 2023
    jeepstar

    jeepstar Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Sheboygan
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    I appreciate the quick fix approach, believe me, but I don't want to carry a hammer with me for starters and generators
     
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  7. Oct 3, 2023
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Hills of NH
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    I find they are handy for transmission linkages, and carb floats, too.

    You mean to tell me hammers don't fix everything.jpg
     
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  8. Oct 9, 2023
    jeepermc

    jeepermc Active Member

    Western WA
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    I tried the hammer approach on the FC alternator this weekend... Didn't work. New one already in place and charging. lol
     
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  9. Oct 9, 2023
    dozerjim

    dozerjim Member

    western New York
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    All the above x2...and always have a hammer...:study:....definetly find a shop that can work on generators, usually in farming areas you can find a shop that does electrical repairs that still can work on a generator and test a regulator.
     
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  10. Oct 9, 2023
    jeepstar

    jeepstar Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    All right, went to the tonight to pick up my generator, they said we won't get to it for a few weeks. I said no, I was told when I dropped it off last week it would be done by Wednesday. They said well we could possibly have it done by this Wednesday. I said thanks, but no thanks. Took it home.

    Installed a new ribbed v-groove belt and all seems right.
     
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  11. Oct 9, 2023
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    More red flags on that shop!
     
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  12. Oct 9, 2023
    jeepstar

    jeepstar Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Sheboygan
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    Yes, indeed. They don't do automotive stuff normally but I played the "aw, shucks" guy and they were willing to reluctantly help, but it would be on their schedule. Ain't nobody got no time for that!
     
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  13. Oct 10, 2023
    dozerjim

    dozerjim Member

    western New York
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    x2....not to nit pick, but did you get a belt wide enough, that makes a difference too.....?
     
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  14. Oct 10, 2023
    jeepstar

    jeepstar Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    1/2 x 43 3/8 Dia is the size I have. It's slightly shorter than the worn out one, but plenty of travel in my tensioner arm. Other difference is this new one is ribbed, other one was not.
     
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  15. Oct 10, 2023
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    IIRC, 5/8" wide is the OEM spec in most cases. For future reference I think "cogged" is the correct term, rather than ribbed.
     
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  16. Oct 11, 2023
    dozerjim

    dozerjim Member

    western New York
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    (y) :study:
     
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  17. Oct 11, 2023
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    The operating principle of a v-belt is friction on it's sides, with a minimum of tension. A narrower belt may tend to 'bottom out' in the pulley groove, negating the wedge effect and leading to premature slippage.
     
  18. Oct 14, 2023
    jeep2003

    jeep2003 Well-Known Member

    Upstate NY
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    From my understanding cogged belts are intended for applications where there is a tensioner and the belt gets bent backwards. Makes it less likely to crack over time. But you can still use it without.
     
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  19. Oct 19, 2023
    jeepstar

    jeepstar Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    To recap, I Uninstalled the the generator, put a new cogged belt in place of the worn out one, installed the generator and charged the battery overnight.
    I drove about 20 miles last night, no Amp light, and drove to work today, no Amp light.

    I hope the problem is solved.
     
    Last edited: Oct 19, 2023
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  20. Oct 19, 2023
    Keys5a

    Keys5a Sponsor

    Florida Keys
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    Does the amp light come on before you start the engine (ignition switch to “run”)? It should be lit with the ignition on, then start the engine, and it should go out once the engine is up and running. This condition means the charging system is working. When the amp light is lit with the engine running, the charging system is not working properly.
    -Donny
     
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