Register now to get rid of these ads!

Technical HELP. 6v positive ground 1940 mercury flathead charging issue

Discussion in 'The Hokey Ass Message Board' started by Blake84, Feb 28, 2020.

  1. Blake84
    Joined: Feb 4, 2012
    Posts: 738

    Blake84
    Member

    I have a 1940 mercury with a 6v positive ground system

    I currently replaced the generator with a rebuilt one and also replaced the regulator on the fire wall. I figured I would start the car and boom I'd be back up and charging. I'm currently only getting 6.5v max.

    I flashed the regulator while the car was off removing the field wire to the regulator and touching it to the battery terminal until a spark and then hooking field back up and that did nothing. I tried that 2 to 3 times.

    I am currently stumped and trying to figure out why I'm not charging with new parts.

    Are there some tests I should do to the generator or regulator? If using a volt meter on 6v please be specific because the positive ground things confuses me. Not sure if I could use the positive part of the volt meter to the ground and then negative part of volt meter to the power

    Thanks for any help.


    Here is a video if you see anything that looks wrong
     
  2. Budget36
    Joined: Nov 29, 2014
    Posts: 7,218

    Budget36
    Member

    6.5 volts via meter or gauge? Is the ammeter not used? If it is still there, what doe it do?
     
  3. Boneyard51
    Joined: Dec 10, 2017
    Posts: 5,170

    Boneyard51
    Member

    Here’s an old back yard test, apply 6 volts to the output post of the generator with a set of jumper cables, with out the belt on, and see if it spins. If it does, your problem is not the generator! Might not tell you what wrong, but it can tel you what’s right!









    Bones
     
    Last edited: Feb 28, 2020
    Truck64 likes this.
  4. plym_46
    Joined: Sep 8, 2005
    Posts: 4,018

    plym_46
    Member
    from central NY

    If you temporarily ground the field terminal on the Genny, with the engine at a fast idle, it should peg the ammeter to full charge. This confirms gen is good, so fault is likely at the VR. If your battery is fully charged and all you are running is the ignition the cut out circuit will not be demanding a heavy charge rate. What happens when you turn on the lights and or hi beams? Don't leave the jumper wire on the field terminal longer than necessary to do the test. What size primary battery cables are you using??
     

  5. Blake84
    Joined: Feb 4, 2012
    Posts: 738

    Blake84
    Member

     
    Boneyard51 likes this.
  6. Truck64
    Joined: Oct 18, 2015
    Posts: 5,077

    Truck64
    Member
    from Ioway

    Generator charging systems are simple as it gets. Don't let it kick your ass. Usually when these things come up what happens is someone here will type up detailed troubleshooting instructions, and the OPs eyes glaze over and he goes and picks up an alternator.

    @squirrel has a web page with some generator info. I would suggest studying that, the Shop Manual for your car, and old MoToRs Repair from the period. The troubleshooting trees are usually pretty good. Just keep the Ford/Mercury type "B" charging circuit in mind.

    The idea is to isolate first the trouble to either the regulator or the generator. I would suggest also getting used to the idea of using the analog type of meter. A digital unit will work for just checking voltage output, but it will display gibberish when you start getting into it more in depth. I will say once everything is first setup according to Hoyle they work fine, usually people slap on stuff that's been laying around in the weeds.

    Don't try to "adjust" the regulator. If it's a modern repro, that may be the problem. Good old school NOS or serviceable used regulators.
     
    Boneyard51 likes this.
  7. jaracer
    Joined: Oct 4, 2008
    Posts: 1,220

    jaracer
    Member

    Pretty sure on a Ford you have to supply power to the generator field to get the generator energized. You ground the field on GM products.
     
    Boneyard51 and studebaker46 like this.
  8. jaracer
    Joined: Oct 4, 2008
    Posts: 1,220

    jaracer
    Member

    You say you are getting 6.5 volts max. Where are you measuring this? You may want to measure the voltage at the armature wire on the regulator and at the battery wire. The voltage regulator contains a cut-out relay. It's job is to disconnect the generator armature from the battery when the voltage output of the generator drops below battery voltage. If you have higher than battery voltage at the armature wire, but not on the battery wire, the cutout relay isn't working. This is a problem I have run into with the voltage regulators available today.

    You can full field the generator by disconnecting the field wire at the regulator and touching it to power, in this case battery negative. If you get 7 or 8 volts a the battery negative terminal, the generator is working and you problem lies in the regulator or wiring. If not, the generator is the problem.
     
    Boneyard51 likes this.
  9. Blake84
    Joined: Feb 4, 2012
    Posts: 738

    Blake84
    Member

    Last night when I checked the voltage at the armature wire on the regulator it was like 3.5v or something. That made me think the generator isnt functioning properly

    I just installed it yesterday and it's a rebuilt one that's been gonna shelf for I'm sure many years

    What steps should I take to test generator or "charge it up" or whatever it's called
     
    Boneyard51 likes this.
  10. squirrel
    Joined: Sep 23, 2004
    Posts: 49,793

    squirrel
    Member

    I wonder if the regulator contacts are oxidized from being on the shelf for so long?

    Cleaning them is tricky, you need to get the oxidation off, but not damage them, or bend the adjustments.

    http://selectric.org/manuals/generator/index.html

    .
     
    Boneyard51 likes this.
  11. Boneyard51
    Joined: Dec 10, 2017
    Posts: 5,170

    Boneyard51
    Member

    Yes, but make sure your belt is off, the generator will “ motor” but not as fast as a starter, but will spin at a nice rate and smooth if the generator is good. A rock solid test of a generator.

    Also brushes can stick in a generator, especially one that has set on the shelf for years. Make sure they are movable.




    Bones
     
    Last edited: Feb 29, 2020
    Truck64 likes this.
  12. Truck64
    Joined: Oct 18, 2015
    Posts: 5,077

    Truck64
    Member
    from Ioway

    I won a rebuilt 30 amp generator at auction from EvilBay, a couple few years ago, the sticker said 1989.

    It did work, and sported a nice coat of paint, though among the defects found, the new brushes were installed as supplied, i.e. "square". I didn't catch this because it was rebuilt, after all.

    That's what I pay people good money for, instead of doing it myself. Their expertise, attention to detail, and their pride in workmanship. Yeah, yeah I know, take another bong hit - that's the idea, anyway.

    New generator brushes require sanding so that the surface conforms to the commutator and presents a full contact patch for good current transfer. Normally carbon brushes last a long time, thousands and thousands of miles. These arc'd and burned within just a few hundred miles.
     

Share This Page

Register now to get rid of these ads!

Archive

Copyright © 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.