overcharging

Discussion in 'Mack Forum' started by Bradk, Apr 7, 2013.

  1. Bradk

    Bradk Bobtail Member

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    Apr 7, 2013
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    Gday guys

    we are having problems with a our 98 ch it cooked the alt we put new one on and its cooking batteries. 14.4 volts at idle then16+ at revs surely couldnt be voltage reg in brand new delco. It does come up now and then with a j link code and a pid code,i know j link is main loom and could be a plug but would a short cause overcharging??:biggrin_25510:
     
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  3. daf105paccar

    daf105paccar Road Train Member

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    just to cover the basic but did you check the diameter off the beltwheel?
    Is it the same as the old one?
     
  4. CondoCruiser

    CondoCruiser The Legend

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    If it was me I would remove all the cables off the batteries and check each one's voltage. You might have a dry cell in one shorting out. That happens easily when they got overcharged by the previously bad alternator. You can clean up the posts at the same time. A bad battery will read significantly lower.

    Then I would start checking grounds starting with the main ground off the battery. Any corrosion or a hair loose can cause voltage surges.

    Then I would isolate the alternator hot and see if it's putting out more than 14.4V without any possible load hooked to it. The truck can run off the batteries for a few seconds while you check it. There's bad new parts sold everyday or possibly a bad battery just fried the diodes in the new one which you could exchange.

    Last, if you are relying on the truck's voltmeter for a reading the gauge itself can be bad.
     
  5. Bradk

    Bradk Bobtail Member

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    Apr 7, 2013
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    Cheers i will check that in the morning
     
  6. Bradk

    Bradk Bobtail Member

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    Apr 7, 2013
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    all batteries have been checked but will do it again to be sure. multi meter says the same as the voltmeter,done all the basics with old alt but haven't had a close look at earths yet. cheers for the quick response guys
     
  7. Hardlyevr

    Hardlyevr Road Train Member

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    If you have a 3 wire alternator, the 3rd small wire is the voltage sensing one. If it is corroded inside of a connector, or anywhere along it's path, the alternator will think the voltage is low, and open up the regulator and give you the high voltages. Some alternators are built that if you disconnect that wire, or install on a 2 wire truck, they will only produce 13.8. So you might want to try that. If your batteries check out, and experimenting with the 3rd wire does not help, you may have just gotten an alternator with a bad regulator.
     
    CondoCruiser Thanks this.
  8. snowwy

    snowwy Road Train Member

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    i've seen bad batteries ruin a brand new alternator. replace the battery and the ruined alternator ruins the new battery. replace the alternator which gets ruined by the ruined battery.

    voltage doesn't always drop. some bad batteries will actually take the surface charge where it all accumulates and exceeds thresholds. in other words. they can read high also. common problem if cells are less then full on liquid and cells are warped and shorting out.

    i had that problem on an end dump. batteries actually burst open. but not much water came out. mechanics brought out new batteries, voltage still too high. changed alternator. went back to work.

    warranty the alternator, AND change the batteries.
     
  9. Pedigreed Bulldog

    Pedigreed Bulldog Road Train Member

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    The alternator in my '01 CH is externally regulated....so that new alternator you bought probably didn't include a new voltage regulator.
     
  10. chalupa

    chalupa Road Train Member

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    Good call Hardlyevr....I have the same dog and had the same problems.......

    This dog uses a 24SI single wire and mine has an extra ground offered from the harness.

    My gal whooped my arse to the tune of 3 batts and 3 starters , a solonoid, cables and an alternator.


    Brad, Forget the dash guage, get a solid multi meter and start at ground zero with the batts. Get them load checked too. Check that ground lug on the side of the E-7. It's low and right of the cartridge oil filter below the starter.

    Check that pain in the arse solonoid up on top of the firewall. It's hooked to the windshield washer motor mounting plate. Needs a ground too.

    And last verify that alternator. I got sick of remans and bought new delco stuff from dog. I also added a 00 cable from batt to frame,and frame to starter.

    JMO
     
  11. Ridgeline

    Ridgeline Road Train Member

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    Just to add, check your grounds, there should be a ground strap from the alternator to the engine block.
     
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