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  1. #1
    Silver Member
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    Aug 2007
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    Default Ignition Switch or??

    Hello,

    I'm wrestling with a few gremlins on my 3910; right now, I'm dealing with what I hope is just an ignition switch issue (as opposed to a potentially more complicated and harder to diagnose electrical issue). Here's what's happening:

    When the tractor is off, the dash lights are powered up (horn works too, haven't check headlights but I assume they'd work too) no matter what the position the key is in. Once I start the tractor, all the lights go off. But when I shut it back down, everything stays on and slowly drains the battery.

    For the time being, I am simply disconnected the neg cable on the battery, but I definitely want to fix this issue.

    I'm planning to start by replacing the ignition switch, since it's cheap and simple. But I'd like to get ideas on what else I might troubleshoot, or if it's obvious to anyone that this is NOT a problem with the switch.

    Thanks.

  2. #2
    Elite Member mostly_gas's Avatar
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    Sep 2009
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    Texas
    Tractor
    in-between tractors

    Default Re: Ignition Switch or??

    From the symptoms I would be more inclined to look at the voltage regulator and related wiring. Try unplugging the regulator and see if the key controls the gauges, light etc better.

  3. #3
    Platinum Member Qapla's Avatar
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    Sep 2008
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    907
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    Gator Country
    Tractor
    New Holland TC40D HST 4WD FEL/BH

    Default Re: Ignition Switch or??

    I would also check the chassis ground and make sure that the neg bat. cable is making good contact with the frame.
    New Holland Workmaster 45 2WD Gear
    Massey Ferguson 240
    New Holland TC40D HST 4WD
    NewHolland 16LA FEL
    Woods BH 70-X Sub-frame Backhoe
    Troybuilt Super Bronco w/42" mower
    Husqvarna DRT 900 Tiller
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    Husqvarna HU625WT String Mower

    3 point hitch attachments:
    single plow, double plow, 5' & 6' deck mower, tiller, 2 cultivators, planter, fertilizer spreader, disk set, sprayer, and a few homemade attachments

    30 acres, 15 acres, 5 acres

  4. #4
    Epic Contributor
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    jinman's Avatar
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    Texas - Wise County - Sunset
    Tractor
    NHTC45D, NH LB75B, Ford Jubilee

    Default Re: Ignition Switch or??

    Have you owned the 3910 since new? Is this a new problem that just developed? It sounds like you may have a short somewhere that is connecting your light circuit to the hot battery bus. If someone previously owned the machine, they might have done a wire modification. You also could have 'mouse modifications' to the circuits.

    Your ignition switch can be checked pretty easily by removing it and running continuity checks when it is turned off. Does your engine stop when you turn the key to off? If it does, then your ignition switch is probably okay.
    Jim


  5. #5
    Silver Member
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    Aug 2007
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    108

    Default Re: Ignition Switch or??

    Thanks, everyone. The tractor is fairly new to me; I've put about 50 hrs on it in the few months I've owned it. This issue just cropped up.

    Jinman, this tractor has a fuel shutoff cable to stop the engine. In other words, no, it doesn't stop with the key, but it's not designed to.

    I'll try the other suggestions and report back. While I'm halfway decent at basic wrenching duties, I'm also one of those poor saps who really struggles with electrical stuff. Maybe this will be a good opportunity to improve my skills!

    Anyway, thanks again!

  6. #6
    Silver Member
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    Default Re: Ignition Switch or??

    So in the process of removing the ignition switch to run some tests, I fiddled with the wires a bit and got it working. Seems like there's a suspect contact at one of the terminals or perhaps even inside the switch. Anyway, it's working for now, and I've got a pretty good idea where to start if the problem crops up again.

    Now onto my other little fixes: Broken tach adapter and broken fuel shut off cable. All three - the switch, the tach, and the fuel shut off - crapped out in the same week!

    Thanks, everyone.

  7. #7
    Old Timer Soundguy's Avatar
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    Mar 2002
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    51,751
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    Central florida
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    ym1700, NH7610S, Ford 8N, 2N, NAA, 660, 850 x2, 541, 950, 941D, 951, 2000, 3000, 4000, 4600, 5000, 740, IH 'C' 'H', CUB, John Deere 'B', allis 'G', case VAC

    Default Re: Ignition Switch or??

    if i found it was bad.. I'da replaced it before putitng back in... just sayin....

  8. #8
    Silver Member
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    Default Re: Ignition Switch or??

    I would've, but I have the cluster out anyway, to replace the fuel shut-off cable. So while I wait for the cable to arrive, I'll have a few days to see if it's working with things still torn apart.

  9. #9
    Old Timer Soundguy's Avatar
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    Mar 2002
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    Location
    Central florida
    Tractor
    ym1700, NH7610S, Ford 8N, 2N, NAA, 660, 850 x2, 541, 950, 941D, 951, 2000, 3000, 4000, 4600, 5000, 740, IH 'C' 'H', CUB, John Deere 'B', allis 'G', case VAC

    Default Re: Ignition Switch or??

    wow.. had to pull the cluster for the stop cable? they must have moved them. didn't have to do that on a 3000 i worked on.

  10. #10
    Silver Member
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    Aug 2007
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    108

    Default Re: Ignition Switch or??

    Yeah, to get the nut off the backside of the dash... pretty easy, actually... four screws and it just pops out.

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