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Technical Testing generator?

Discussion in 'The Hokey Ass Message Board' started by oldnuts, Oct 24, 2015.

  1. oldnuts
    Joined: Jan 14, 2009
    Posts: 355

    oldnuts
    Member
    from nebraska

    can you test a generator while it's still on the engine? If so how? Thanks
     
  2. oldnuts
    Joined: Jan 14, 2009
    Posts: 355

    oldnuts
    Member
    from nebraska

    Without having a voltmeter or a working volt meter gauge?
     
  3. llonning
    Joined: Nov 17, 2007
    Posts: 680

    llonning
    Member

    If everything is good, you should be able to remove the belt and turn on the key and the generator should motor. If it doesn't something is wrong. Just the way I tested them on the engine too many years ago.
     
  4. Budget36
    Joined: Nov 29, 2014
    Posts: 8,444

    Budget36
    ALLIANCE MEMBER

    Been years since I motored a generator, but pretty sure the way you describe won't work, I recall having to pull a wire off and jump something.
     

  5. oldnuts
    Joined: Jan 14, 2009
    Posts: 355

    oldnuts
    Member
    from nebraska

    Can you explain motoring? The truck will run fine but the battery won't charge and the electrical system is my biggest enemy.
     
  6. F&J
    Joined: Apr 5, 2007
    Posts: 13,221

    F&J
    Member

    What brand of car....because of how you jump the field wire...

    if FORD only, a working generator will produce, if you put a HOT jumper to the FIELD terminal

    all other like GM and Mopar, you jump the field terminal to GROUND

    You should only do this with wires removed at the generator. Now put a voltmeter to the BATT or + terminal on generator. Then jump the field terminal while engine is at driving RPMs, but only jump long enough to see if the volts go way beyond the normal battery voltage. Jumping the field makes a generator run "wild" to very high voltage, so do it quickly.

    I use an older analog meter with the needle, but it should also get a reading with a digital, I assume.
     
  7. J. A. Miller
    Joined: Dec 30, 2010
    Posts: 1,779

    J. A. Miller
    ALLIANCE MEMBER
    from Central NY

    Oldnuts,
    If you are working on cars, you should have a voltmeter. They aren't expensive - hell Harbor Freight gives them away sometimes. Just sayin
     
    oldnuts and bobkatrods like this.
  8. F&J
    Joined: Apr 5, 2007
    Posts: 13,221

    F&J
    Member

    Hey, what about the poor mans way of seeing if there is more than 6 or 12 volts, .....

    When jumping the field, you are supposed to see perhaps two times or more, the normal voltage at around 1200 or 1500 rpms. So, what about using a small car light bulb, to see if the bulb burns out instantly? Just use a 12 v bulb on a 12v gen, or 6v bulb on a 6v generator....it should burn out quick.

    if it barely glows in the dark, that is likely only a couple of volts like you would see with shorted fields. ---or it may not glow at all. Just make sure the bulb works on the battery first
     
  9. llonning
    Joined: Nov 17, 2007
    Posts: 680

    llonning
    Member

    Sorry for the delay, busy in my shop. Motoring is when you supply electricity to the generator. If everything is good the generator will spin on it's own. When you spin the generator that is when it will produce electricity, then provided everything is good it will charge.
     
  10. oldnuts
    Joined: Jan 14, 2009
    Posts: 355

    oldnuts
    Member
    from nebraska

    I've got a voltmeter but I've loaned it to a friend last week and he's out of town. It's a 63 ford yblock. I'm charging the battery and I'll use some of these tips shortly. Thanks fellas
     
  11. Truck64
    Joined: Oct 18, 2015
    Posts: 5,316

    Truck64
    Member
    from Ioway

    So buy a DVM. They aren't expensive and have lots of other uses too. Anyone working on cars (new or old) can't get along without it.
     

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