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Weird problem: alt charging circuit gets disabled

Discussion in 'Truck & Equipment Repair' started by PlowGood, Feb 5, 2009.

  1. PlowGood

    PlowGood Member
    Messages: 48

    Here's the scenario:

    Ford 2003 F250 SD 4x4 gas engine; factory plow package (HD alt and extra cooling etc); Boss plow 2003.

    Three storms ago, blinkers/hazzards blow fuse while plowing.

    Two storms ago, blinkers/hazzards blow fuse again, almost immediately while driving. Start plowing and dash gauges blow fuse. Plowing somehow cause alternator to NOT charge battery. Battery dies. Get jump start. Dies again while limping home (in heavy rain mind you). Jump start again.

    Mechanic says alternator is dead, battery fine. Replaces alternator ($300 parts plus labor).

    Truck is used for other work, towing a trailer/asphalt hotbox. No 4wd used. No issues.

    Plowing 2 nights ago, ten minutes into plowing the gauges go dead. Turn signals still work. I can tell by engine sounds that the alternator is not charging. Plowing with no lights, no radio, no heat blower. Fifteen minutes later, the battery dies.

    Swap sander battery into truck (fun at midnight in 18 degrees), so can finish plowing that property. That battery dies after 15 minutes. Wait for rescue.

    Mechanic now says, that something in the FWD circuits is blowing fuse that kills not only the gauges..... but also causes the alternator to NOT charge the battery.

    How does THAT happen?

    BTW, I'm also thinking maybe the first alternator wasn't dead..... I'm thinking the mechanic didn't check it for this "mystery" circuitry problem. Just saw that it wasn't sending out juice to the battery for charging.

    Mechanic says he has no idea how long it will take to find the real problem, could be shorted wiring when 4WD is used.

    Any ideas?
  2. Lencodude

    Lencodude Senior Member
    Messages: 128

    I had a similar problem like yours on my 88 gmc. The fuse would blow continously and had no heater, 4wd and parking lights. Wiggle the wire at a gas station and it stopped blowing fuses. Bought it to a friends shop and it was a set of wires rubbing on the body near the starter. It had wore threw the plastic wire wrap and exposing the live wires to the body. Wrap the expose wires with electrical tape and problem fixed. Get your mechanic or yourself to thoroughly inspect the wire harness that is touching the frame this can be the cause. If the wire to your alternator is shorted out it will fry your alternator again if not fixed Hope this helps!

    Last edited: Feb 5, 2009
  3. grandview

    grandview PlowSite Fanatic
    Messages: 14,609

    I had the same problem. I think someone told me it has to do with a ground in the shifter ,So someone correct me.
  4. PlowGood

    PlowGood Member
    Messages: 48

    Can you recall more details please?
  5. grandview

    grandview PlowSite Fanatic
    Messages: 14,609

    Not really I had the tranny replaced and it hasn't happened since then.
  6. no lead

    no lead PlowSite.com Addict
    Messages: 1,308

    check your 7 way plug for corrosion between the terminals. if the batt charge wire is shorting, it could kill the batt.
  7. PlowGood

    PlowGood Member
    Messages: 48

    It is not the battery going dead from a "short" that drains the battery..... the alternator charging circuit is blowing the fuse so it does NOT send out power to recharge the battery.
    Last edited: Feb 5, 2009
  8. PlowGood

    PlowGood Member
    Messages: 48

    Anyone have a wiring diagram for this truck? Maybe an online link to a free one?
  9. Acmemechanic

    Acmemechanic Senior Member
    Messages: 137

    Sounds Like Bad Grounds.Ecm Controls the alternator it also depends on Good Ground to operate.Then all The other Systems Act as Grounds When there Is None.Check and Clean all the Grounds.
  10. Gix1k4

    Gix1k4 Senior Member
    Messages: 172

    My '99 f250 did something similar, there is a bundle of wires (3 or 4) on the passenger side inner fender. Check where they join for corrosion. If i remember correctly, the small wire from the alternator goes to that bundle. I had to cut and re-solder that bundle, because it was "disconnecting" the regulator in the alternator, basically telling it to stop charging.

    I don't know if it's the same problem as you're having, but I have heard of one other person having the same issue.
  11. PlowGood

    PlowGood Member
    Messages: 48

    Follow up:

    Last weeks blizzard, same thing. Battery died because alternator wouldn't charge. Limped home on the sander battery, reading 10.5 volts.