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Dreaded "low voltage/dim lights at idle"

Discussion in 'Repairs, Maintenance, Help' started by kzooman83, Oct 7, 2016.

  1. Doug D

    Doug D Virginia Gentleman

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    I had a 1968 Camaro (First car). Even though it did have an alternator, the idiot light still had "GEN" for generator.
     
  2. page2171

    Level 2 Supporter

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    I think my first car (1971 Pontiac LeMans) was the same way.
     
  3. Dave Z

    Dave Z It's me, Dave
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    All these years... well, it'll sure help with bulb replacement!
     
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  4. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    Put in LED bulbs like I did, for 99 cents each, and never have to replace them again.
     
  5. Meester Beeg

    Meester Beeg Active Member

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    I have two motorcycles in which the alternators have permanent magnet rotors.
    Dont produce much at idle but at about 3k it comes on in a rush.
     
  6. schelled

    schelled Well-Known Member

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  7. Rick Anderson

    Rick Anderson Well-Known Member

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    Technically that is still correct.

    Motors can be electric motors and internal combustion engines (piston and turbine). Motor is the more general term.

    Generators can be alternators or dynamo's (both DC and AC). Generator is the more general term.

    Its just that the word Dynamo fell out of use and we call them generators today, especially DC dynamos. So that creates confusion, cause alternators are technically generators also.
     
  8. Dave Z

    Dave Z It's me, Dave
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    I didn't have much luck with tail-lights but will try it for the interior lights, I could sure use more brightness.
     
  9. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    Yes, I've only done it for the instrument panel so far. Can't do it easily for taillights because brake and stop are shared, and I would have to match the load.
     
  10. Dave Z

    Dave Z It's me, Dave
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    I did not have a load issue, you can get around that with electronic blinkers, but the LEDs have to be very carefully chosen since most are not good with light directionality and the numbers on the box can be hokum.
     
  11. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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  12. NYBo

    Level III Supporter

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    I had a set from them in my Dakota's taillights. They worked great. I wish I had pulled them out before I sold them and put them in my Ram. They were around $25 for the pair, IRC.
     
  13. ka9yhd

    ka9yhd Active Member

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  14. ka9yhd

    ka9yhd Active Member

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    My parents bought a 1980 Chevy Citation new and it had a generator light that would flicker dimly at idle.
     
  15. NealXu

    NealXu Member

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    Hi...i am a new user here. As per my knowledge they can build it so the alternator charge well at idle in drive but then they would have greater parasitic losses and more wear and tear at Cruise.It really doesn't depend of the size of the alternator, its the speed of the rotor through the magnetic field in the alternator that have to be high enough.
     
  16. 68RT

    68RT Well-Known Member

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    Having a generator required a rebuild about every 20 to 30k as the commutator would be worn from the arcing that occurs when the brush from one commutator segment to the next. Also, the commutator has real RPM limits as the segments are held in place by friction as they are pressed into place. The field is on the outside of a generator. On an alternator, the field is on the inside eliminating the need for the commutator. Brushes now just slide on slip rings which eliminated arcing giving a much longer life. Also, you can spin it much faster giving greater output at idle speeds. That required two bearings instead of a bearing and a bushing to accommodate the additional RPM along with a much more compact assembly. Good selling point when it came out. They did find that the failure point was the bearings were wearing out and did increase pulley diameter after a couple of years to slow them down. Wasn't much later before they increased amperage to meet increased demands. Chrysler used higher amperage generators in the 50's than the early alternators to help compensate for low idle output. You would be suprised at pulley diameter of early HEMI generators to keep them from over speeding. They really did high revs for the time.
     
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  17. David Eidell

    David Eidell Well-Known Member

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    Here is a cheater's way...

    Your Duster came originally with what is called a SQUAREBACK ALTERNATOR. Look at the case -- between the two halves. See the (approx) 1-1/4" thick steel STATOR LAMINATIONS? MoPar upgraded this alternator in the 1980's with the REVISED SQUAREBACK ALTERNATOR. They are interchangeable if used with an electronic voltage regulator, which the duster has. Same fit, same bolt mounting, same pulley.

    The REVISED SQUAREBACK does not present an inch thick stator. Between the case halves is just a narrow crack. You can see the difference between the two from twenty feet away.

    MoPar offered a 78 (seventy-eight) ampere model of the revised squareback and it is common. Any parts house carries them. Be sure to specify seventy eight amps. There is an improvement to very low speed performance. Close to seventeen amperes more output at 1,600 alternator ROTOR speed RPM. The extra 18 amperes at higher speed doesn't hurt either.

    This alternator uses the same voltage regulator and wiring as your early model. MoPar changed the rotor bobbin fill and increased stator wire gauge one-fourth number thicker.

    I played with these revised squareback units and by virtue of tweaking rotor bobbin fill and using a double wye stator winding, doubled idle output while obtaining 116 amps hot output.

    When I was rebuilding alternators, I must have cured 30+ problems specific to yours simply by fitted the 78-amp revised squareback. The issues were almost all entirely on recreational vehicle motorhomes.

    Hope This Helps
     
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  18. pt006

    pt006 Active Member

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    1960's generators lasted quite a long time. A relative of mine bought a 1961 Ford brand new. The generator was still good at 75,000 when he sold it. That said, it was a 12 volt system in a car that started easily most of the time. The old 6 volt systems had to put out more amps, and the cars spun over slower, causing longer starting times, and more abuse for the generator brushes.

    The internal wiring diagram for my PT Cruiser shows 8 diodes while the older alternators had only 6 diodes. I don't know how it works, but the headlights don't dim at an idle with the high beams on and the radiator fan on high. The radiator fan draws a lot of current, maybe 30 amps.?
     
  19. pt006

    pt006 Active Member

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    Most of the early 1970's mopars had a true ammeter. The current went from the alternator to the battery [this is oversimplified]. It went thru the bulkhead connector, thru the ammeter studs, and back thru the bulkhead connector.

    In the 1980's trucks, they used a shunt system. [oversimplified, again] They used a #6 wire between the alternator and the battery under the hood. Then they ran a # 16 wire in parallel with the # 6 wire and routed it thru thru the fire wall. Most of the current ran thru the #6 wire, and the smaller amount that ran thru the #16 wire was 'ammetered' .
     
  20. David Eidell

    David Eidell Well-Known Member

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    EIGHT RECTIFIER alternators, rectify series (WYE) configured stators. Y. The meeting point of the three coils can either be connected together or rewound then have a positive plus a negative rectifier BRIDGE installed which is the same way all the Y ends of the winding have their own rectifier bridge. The effect improves (increases) low rotor speed output and high speed terminal output. The actual stator winding configuration is slightly different than a standard unrectified Y stator.
    Some alternators have 12 rectifiers. These guys are nothing more than a standard Wye or Delta winding with 2 not 1 rectifier. Meaning the rectifiers are paralleled.
    Hope This Helps
     
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