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Mower trouble

Post in 'The Gear' started by Joful, Jun 5, 2013.

  1. Joful

    Joful Minister of Fire

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    The machine: Deere Z-trak 757 with 60" 7-iron deck

    What happened (in chronological order):

    - Checking engine oil each week, being my anal self, and noting it had been closer to the minimum line than the middle of the range ever since the fall oil change, so added enough oil (1/2 quart'ish) to bring level up to 60% of range on dipstick.
    - Went over machine and cleaned out all grass. Noticed rubber boots were not properly in place on positive battery terminal and generator output terminal. Pushed boots firmly into place. Noted battery positive terminal was showing moderate to heavy corrosion, but did nothing about it.
    - Started machine, all good.
    - Engaged mower deck and noticed battery / alternator light came on. Never seen that before!
    - Shut off deck, alternator light goes out.
    - Ran for several minutes, fiddling back and forth, but continued to see alternator light on any time mower deck was engaged.
    - Shut down, removed both battery lugs, cleaned with emery paper, greased both lugs with antioxidant electrical grease, and reinstalled. No change in symptoms.
    - Said, "F-it, it's getting dark," and proceeded to mow lawn. Alternator light went off after several minutes.
    - Ever since, noticed alt light comes on for several minutes when mower deck is engaged, but often goes back out on its own.
    - Tonight, about two hours into mowing, the mower deck shut off.
    - I re-engaged, and the deck ran a few seconds, then shut off again.

    I have not done any trouble-shooting yet, aside from a quick visual on the wiring. I have not checked the draw on the PTO solenoid, or even located it on the machine, yet. My initial gut feeling was that I probably have a charging problem, but the machine starts with no sign of battery weakness.

    I have noticed since this started, that my seat switch isn't setting off the way it used to, such as if I forget to engage the parking brake before standing up from the seat. This may be related.

    It appears this battery is the old-skool type, not the maintenance-free type I've owned in every car I've ever owned, so that's an immediate suspect. I have checked fluid levels and electrolytic specific gravity on a few batteries in my life, but the last time was probably 20-25 years ago.

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  2. bogydave

    bogydave Minister of Fire

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    Is the battery charged now after all this stuff happened (does it crank & start) ?

    My JD has an electric clutch for the PTO, that engages the mower deck.
    Loose wires, clutch wiring, loose ground.
    solenoid coils got hot sometime & now , insulation breaking down when it gets hot & shorts out.

    Hard to troubleshoot the DC solenoid coil , look burnt/black, melted ?

    Your symptoms are also similar to a loose/bad ground.

    Battery weak & won't handle the added electric clutch current.

    Measure battery voltage, start & see if it's charging. Charging rectifier may be bad or weak.

    Might be some help here: *******
  3. MasterMech

    MasterMech Guest

    For sure check out the charging system basics. Stator voltage (AC output) and overall charging function. Loose grounds, loose connections with the + battery cable, main harness feed, charging sys fuse connections and the key switch are all items I would watch. If you can hook up your meter while you mow, that would be helpful.

    The fact that the problem occurs intermittently and the PTO cuts out would have me checking and wiggling switches and connections after making sure the charging sys and grounds are 100%. And I would be looking real hard at that key switch as it is the only component that affects the charging sys, engine shutdown, and the PTO. ;)
  4. Joful

    Joful Minister of Fire

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    The fact that the light goes out after a few minutes of running the deck, and that I can restart the deck after a few minutes of running (charging), tells me it must be one of two things:

    1. Pto clutch solenoid draw is too high for charging system to keep up.
    2. Charging system output is too low.

    As stated, I can start the mower without trouble, even after three mowings (7.5 hours) running in this state, which perhaps points more at the solenoid than the charging system. Don't know how to find a spec on what that solenoid SHOULD draw, but perhaps I'll find that in the shop manual. Corrosion of connectors is not much of an issue, as the mower is kept clean, indoors, and is only 4 years old.

    Would appreciate some specifics on how you'd debug this. Can't run the mower unless I'm on the seat, unless I make up a bypass connector for the seat switch harness.
  5. smokinj

    smokinj Minister of Fire

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    Can you set the parking brake and hope off? Neighbor 0 turn toro sets and idles often.
  6. Joful

    Joful Minister of Fire

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    I wouldn't say I'm 100% on this, but I think that any time I leave the seat with the mower deck live, the ignition will kill, parking brake or not.
  7. smokinj

    smokinj Minister of Fire

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    Try it, never seen one that didn't work like that. But never been around a Deere Z-trak 757.....
  8. MasterMech

    MasterMech Guest

    That's how it's supposed to work.


    Check for continuity of PTO clutch coil to ground.

    Charge the battery well, disable the ignition system and crank the engine for 5 seconds. Let it sit for about 30 seconds and read the voltage across the battery terminals. This will be your starting reference. Start the machine and run the engine at full RPM's. Note the battery voltage after 15 seconds or so. Should be much higher than your reference. Now hit the PTO, how big of a drop did you get? Still above the reference? (Should be...) Leave it hooked up and mow with it, keeping an eye on it. Does the voltage drop slowly or does the deck just suddenly shut-down?

    The good news is if you have a clutch coil winding shorting out intermittently, there will come a point at which it starts popping fuses and your diagnosis will become much more certain at that point. ;lol
    Joful likes this.
  9. Bret Hart

    Bret Hart Burning Hunk

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  10. lukem

    lukem Minister of Fire

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    Got another battery you can swap in there? Before you go trouble-shooting everything I would swap in a known-good battery if you have one.
    Joful likes this.
  11. Jags

    Jags Moderate Moderator Staff Member

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    A battery that is on its way out can cause symptoms like that. Do as MM said for testing it. After the 5 second crank you should still see a voltage above 12.4V. When you do start and run it, you should see a voltage in the high 12's or low 13V.

    Engaging the PTO clutch shouldn't have much effect on the Voltage output if things are working correctly. (amps, yes - voltage, no).
    Joful likes this.
  12. mellow

    mellow Resident Stove Connoisseur

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    To by pass the butt in seat switch I just put a cinder block in the seat and hop off on my mower.

    I second trying another battery, old batteries can act fine until they are put under pressure, had some strange issues with this on outboard boat motors.
    Joful likes this.
  13. greg13

    greg13 Feeling the Heat

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    Bring it up and I'll check it out for you, it should only take a few years to find the problem with weekly testing:).
    I would bet it is something stupid like a bad connection or switch.
    Joful likes this.
  14. Joful

    Joful Minister of Fire

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    Thanks, guys! I'll definitely make some time Saturday to pull this machine into the shop and have a better look at it. Step 1 will be checking liquid and electrolyte concentrations in the battery, step 2 will be following MasterMech's thought on running it with the meter on it.

    Unfortunately, I do not have another battery small enough to fit in that battery compartment.
  15. Sprinter

    Sprinter Minister of Fire

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    Just thinking out loud here. I would think that if it were the battery, the alt light would come on right after starting and then maybe go out as the battery charges, since the starter must draw more current than the pto solenoid (normally). I'm thinking maybe the pto electrics are drawing too much with shorted coil turns or something like that. Anyway, should be fairly easy to narrow down once you get your dmm on it. Let us know.
  16. Joful

    Joful Minister of Fire

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    Started troubleshooting. Battery appears to be maint free, although its not labeled as such. Voltage at battery is:

    Before starting 12.5
    While cranking: 10.7
    engine full rpm: 14.3-14.4
    Engine at low idle: 13.2
    Mower running 12.5 down to < 12

    Seems to be a pto clutch draw issue. Will try to verify. My clamp on ammeter is AC only, may have to run in to work to pick up a DC clamp.
  17. MasterMech

    MasterMech Guest

    Hook another load to it and see what the charging sys does. 5-7 amps should be plenty to simulate the PTO clutch draw. That charging sys should hold its own up to 20-30 amps easy. Measure Stator AC output at the regulator - should be about 28v AC give or take. (At full RPM)
  18. Joful

    Joful Minister of Fire

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    Well, clutch coil measured less than 0.4 ohms, should be 2.0 ohms, so I picked up another clutch ($ yikes! $). Going to install it now. Will check unregulated stator, as well. Not sure I have another DC load that size handy, unless I steal some of the lights off my tractor.
    ScotO likes this.
  19. Joful

    Joful Minister of Fire

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    Fixed! Diagnosis: bad clutch coil. Cost: $325 + tax

    Thanks for all your help, guys!
    ScotO likes this.
  20. Sprinter

    Sprinter Minister of Fire

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    Glad you got it. Expensive, though...
  21. bogydave

    bogydave Minister of Fire

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    Just for kicks, did you notice what caused the clutch to go bad?
    Get hot? wet?
    Look burnt?
    ScotO likes this.
  22. Joful

    Joful Minister of Fire

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    Deere green paint adds $250 to the cost of any common part.

    Do note that the clutch was fine, it was the clutch coil (think solenoid) drawing too much current that was the trouble. Didn't disassemble to debug, as replacement coil was only available as a complete clutch assembly. Kept indoors, not used in wet conditions, less than 500 hours, so who knows? Maybe just a fluke.
    MasterMech and smokinj like this.
  23. Sprinter

    Sprinter Minister of Fire

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    LOL. So I'm told.

    Edit: It's the same with Harley black
  24. Joful

    Joful Minister of Fire

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    I forgot to mention, local dealer had three of these clutches in stock. Must be a common failure.
    ScotO likes this.
  25. MasterMech

    MasterMech Guest

    Actual clutch/coil failure is not really a common failure on low-hour examples like your machine. But it is on high hour, heavily used/abused commercial units and those guys really dislike waiting for parts. ;)

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