Strange electrical behaviour

Electrical & Ignition

  1. Marv

    Marv Wannabe C-body owner

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    Following Problem on my 68 Poncho.. I know it´s not a Mopar but I figure that the way our electric circuits work are kinda equal, so I hope some experts might help

    Two weeks ago my generator warning light turned on.
    So I measured the voltage at the battery -> ignition off -> 12,8V -> battery good..

    Thereafter engine on, transmission P, automatic choke increased the rpm (don´t have a rpm gauge so I don´t know the value) -> voltage increased slowly to 14,1V max -> turned choke off -> rpm back to idle -> voltage decreased to 13,8V -> good , alternator is working and charging the battery....

    thereafter, trans still in P -> gaspedal halfway down -> 15,1V -> not so good -> gaspedal 3/4 down -> 17,4V -> not good at all ..

    I figured the voltage regulator to be the bad guy and ordered a new one.
    Today I installed it, measured the voltage the same way I did before and it was all fine, max value was 14,5V.
    But then I wanted to go for a ride and as soon as the trans was in D and I had the Gaspedal halfway down, the warninglight came rght back on accompanied by a not very loud but very audible humming from somewhere underneath the dasharea. As soon I went off the pedal the humming disapeared and the light turned off. I had no time to find the origin of that noise, but that´s new.
    Any ideas what the new poblem might be or what´s the best way to figure it out is higly appreciated
     
  2. Marv

    Marv Wannabe C-body owner

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    This is the old VR. It has major corrosion on the F and 2 port. Nothing on the 3 and 4 port. Internally it looks like new, so I figure that might have been the problem in the first place. Now with the new VR, is it possible that the connector metal inside the plug has also corrosion on it (which sure is the case) so that the current still doesn't flow as it should and that causes the problem?

    _20190706_162647.JPG
     
  3. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

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  4. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    As John said, clean up the terminals before going any farther. I would temporarily reinstall the old regulator and see if you still have the hum. A regulator will sometimes hum of the points are opening and closing very rapidly, usually due to a short some place in the wiring, a poor connection could also do this. Also check to be sure the regulator has a good ground. Also check the terminals to the generator to be sure they are tight. At 17v, you old regulator probably had stuck points, check to see if they move freely. Fused points in the old regulator usually indicated a short in the battery or a short in the wiring for the charging circuit. Corroded terminals cause high resistance which make it impossible for the regulator to function properly, with the points opening and closing rapidly (humming), it is only a matter of time until they heat up and fuse.

    Dave
     
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  5. Marv

    Marv Wannabe C-body owner

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    Thank you both! I'll try to clean up all metal connections first and check for proper ground! That regulator sits at the firewall right behind the air cleaner, so far away that it's a pain to work on it and I'm 6'4" tall..
    The plug is a real problem, it's shape is kinda unique so I've to get it going as replacing is not an option.
    Thanks for the advice to clean and reinstall the original regulator, that might be a good double check if the new one is bad..
     
  6. 1970cat

    1970cat Senior Member FCBO Gold Member

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    check for corrosion at the pins on the alternator too. corrosion can cause false signals to be sent to the regulator.
     
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  7. Marv

    Marv Wannabe C-body owner

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    Pins at the alternator look good. I checked again today. Scratched the paint off the firewall to make sure it hits bare metal for good ground.
    The humming is the VR vibrating, as Dave suspected.
    Took the new VR off and opened it. No fused points but the one in the front was very tight, almost no spacing. That's the only difference I can find between new and old VR. So I bend the bracket a little, now I've got about 1,5 mm spacing. Maybe that's it. I'll give it a shot tomorrow, don't want to provoke a neighborhoodwar by firing up the engine 10 times on a Sunday
     
  8. Marv

    Marv Wannabe C-body owner

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    I can't spot any difference. Cleaned now the old one and install it back tomorrow

    _20190707_102504.JPG

    _20190707_102520.JPG
     
  9. Big_John

    Big_John Illegitimi non carborundum FCBO Gold Member

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    I'm actually kind of surprised the new one isn't electronic. I don't think you can buy an over the counter mechanical VR for a 60's Mopar these days.
     
  10. jct

    jct Senior Member FCBO Gold Member

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  11. Marv

    Marv Wannabe C-body owner

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    So an update on the situation.

    Cleaned and reinstalled the old VR. Starting the engine, choke increases RPM, voltage at the battery increases
    through 17 V before I shut the engine down again..
    Installed the new one with the modified points, starting engine, RPM rises, voltage at the battery is between
    14,5 and 15V and remains there. Shutting the choke down, rising RPM manually voltage remains around 14,8V, then
    dropping RPM to idle and the voltage rises above 17 V ...

    I don´t get it, 2 VRs 2 different kinds of misbehaviour ... are both bad or is maybe the alternator the real bad guy ?
    Or did I fry the new one when it was installed first with the points too close !?
     
  12. 1970cat

    1970cat Senior Member FCBO Gold Member

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    17v is full field for the alternator. 14.8 is acceptable under load. i think your alternator is fine.
    does anyone have a known working regulator you could try?
     
  13. Marv

    Marv Wannabe C-body owner

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    I'll order an electronic one next and see what happens then. I think as the two VRs are showing different kinds of malfunction, the alternator should be fine and I have two broken VRs