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  1. #1
    Platinum Member
    Join Date
    Mar 2005
    Posts
    947
    Location
    central Illinois near Lake Shelbyville
    Tractor
    Case 2090 Massey Ferguson 4233 John Deere 4700

    Default Altenator question

    I went to start my tractor Saturday and it had to be jumped. I tested the Batteries and they both tested bad. I replaced them and it started like always. Tonite I had it running at a idle for a few minutes and when I went to shut it off the Battery light was on real dim. Hooked my meter up to the batteries all is good. Started it and checked the charging system all is good. Turned on the headlights and all is good. Shut the lights off and the needle went to 15 volts and stayed there. Battery light on the dash was dim. I can make the light go out by speeding up the engine. If it was daylight you would never see the light. Is 15 volts a little too much. Never noticed the light before the battery change.

  2. #2
    Platinum Member KYErik's Avatar
    Join Date
    Dec 2005
    Posts
    503
    Location
    Kentucky
    Tractor
    1963 Ford 4000, 1943 Case SC, Case 530CK backhoe

    Default Re: Altenator question

    15 volts is a little bit high- I think 14.5 volts should be about as high as it should go.

    What was the voltage when the dash light went out (when you revved the engine)?

    To high of a voltage can heat up the batteries and bake out the water- were the old ones still full of electrolyte?
    "Attitudes are contagious; is yours worth catching?"

  3. #3
    Platinum Member ModMech's Avatar
    Join Date
    Dec 2009
    Posts
    684
    Location
    Canton, TX
    Tractor
    Kubota B2410

    Default Re: Altenator question

    Normal charging voltage for an alternator with a "12V" system is 13.6V Min to 14.5V max although most are capable of over 15V as you have discovered, it is TOO HIGH.

    Check the voltage with the lights on and the tractor at 1200 RPM both at the alternator terminals and battery terminals. The voltage measured at the alternator and battery seperately must be within 1/2V of each other or you have a wiring problem. If that checks out, but the voltage is higher than 14.5, the regulator has failed (internal or external).
    JohnG
    We have Democracy, but were founded on Liberty.
    Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote - Benjamin Franklin (1706-1790).

    I am for LIBERTY!

    I Support electric trailer brakes on EVERY axle over the towing vehicle's GVW, CDLs for RVers and safety inspections on ALL licensed vehicles!

  4. #4
    Gold Member
    Join Date
    Apr 2002
    Posts
    327
    Location
    jackson tn
    Tractor
    Allis Chalmers 416S John Deere LX280, John Deere Z225 zero turn yanmar 1401 , Oliver 550 Special, Oliver 75 Lawn Tractor, New Holland 3930 4WD, Mitsubishi BDF2 Dozer

    Default Re: Altenator question

    I had a similiar problem with my 4WD NH 3930. The tractor was equipped with a Delco alternator (internal reg.). The alternator went bad and I had it rebuilt. The rebuilt alternator was putting out 14.7-15 and the alternator light would flash and the battery would heat. With the lights on the voltage would drop to 14.3 and the alternator light would go off. The rebuilder tried to find another regulator without luck. I bought a new aftermarket alternator and problem solved and now voltage reading 13.7.
    red

  5. #5
    Platinum Member
    Join Date
    Mar 2005
    Posts
    947
    Location
    central Illinois near Lake Shelbyville
    Tractor
    Case 2090 Massey Ferguson 4233 John Deere 4700

    Default Re: Altenator question

    Thanks for the input on this. I went back out and checked all the connections at the altenator and batteries and retested every thing. Same thing as before. Charging system was running at 14 volts without lights off and at 14 with the lights on. I shut the lights off and the needle jumped to 15 volts. After a couple of minutes it dropped back to 14 and the light stayed off. I did this at 1200 rpms.

  6. #6
    Silver Member
    Join Date
    May 2006
    Posts
    245
    Location
    Illinois
    Tractor
    4310 JD 2003

    Default Re: Altenator question

    I have available for sale a 40 amp alternator from a 4310 JD. I went with a 55 AMP.
    Any interest. PM me
    JD 4310
    Stuff, lots of stuff

  7. #7
    Elite Member BobRip's Avatar
    Join Date
    Sep 2004
    Posts
    4,335
    Location
    Powhatan Va.
    Tractor
    2000 Power Trac 422

    Default Re: Altenator question

    Quote Originally Posted by deere755 View Post
    Thanks for the input on this. I went back out and checked all the connections at the altenator and batteries and retested every thing. Same thing as before. Charging system was running at 14 volts without lights off and at 14 with the lights on. I shut the lights off and the needle jumped to 15 volts. After a couple of minutes it dropped back to 14 and the light stayed off. I did this at 1200 rpms.
    I don't think a short time at 15 volts is going to hurt anything. If you are not loosing a lot of water from the battery you will be fine.
    Bob Rip
    Tell me and I will hear.
    Show me and I will see.
    Let me do and I will learn.
    Let me fail and I will understand.

  8. #8
    Elite Member jonyyuma's Avatar
    Join Date
    Sep 2010
    Posts
    2,972
    Location
    35 miles North of Memphis,TN
    Tractor
    kubota L3000dt, ford 8n1952

    Default Re: Altenator question

    If it is over charging you will notice sulfur odor and gassing from the caps or vents? heavy overcharging will cause a bulge in battery. I caused one of these alternators to do this by jumping and it blew out the diode bridge causing swelling...Be very careful of polarity..
    Okay, Legal disclaimer: Old but not senile, definitely do not have the answer to everything!

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