Does anyone think I don't need a new clutch?

Discussion in 'Mechanic and Repair' started by AlohaMowing, Sep 17, 2011.

  1. AlohaMowing

    AlohaMowing LawnSite Member
    Messages: 58

    Before I spend $300 for a new electric clutch, I thought I'd bounce this off those of you who know more than me. If there is anything else to check out before spending the money, I would like to do so.

    I have a Scag Turf Tiger with about 600 hours on it, model STT52V-27CH, serial # B6200001 series, that seems to be going through a series of electrical problems. It now is blowing a fuse a couple seconds after I pull the PTO switch to engage the electric clutch. The clutch is an Ogura GT 3.5. I have done the tests described at Air gap is good at .015. Electrical measurements, however, are not withing specs. The test shows resistance of 0.2 ohm; resistance is supposed to be 2.8 - 3.2 ohms. The current draw is supposed to be "approximately 4.0 amps." My meter, when set for 10 amps DC, is not returning any reading, however the wires get extremely hot to the touch within a few seconds of being energized for the test.

    When I disconnect the plug feeding the clutch and pull the PTO switch with the engine running the fuses don't blow, but if I then connect the plug the clutch starts to engage and within 2 seconds the fuse will blow.

    Thank you for reading, and for any comments.
  2. knox gsl

    knox gsl LawnSite Fanatic
    Messages: 6,255

    Sounds like you have a bad coil in your clutch, not sure if they are avalible seperate of if you have to buy the whole assembly.
  3. LouBraun

    LouBraun LawnSite Member
    Messages: 6

    With a resistance reading of 2 ohms, the coil is likely internally shorted so that many of the coil's windings are bypassed. This would result in the clutch not pulling-in when energized and would also cause high current draw.

    The fuse blowing indicates high current draw even if it is not indicated on your ammeter. It is possible that the ammeter is being over-ranged.

    You can disassemble the clutch and examine the coil and the coil's lead wires. Depending on the clutch's field construction, there is an outside chance that you can see the coil and possibly find the short. If one of the coil lead wires is shorted to the coil windings, just tape up the shorted area and try to see if it works. There is nothing lost in tearing that critter apart since it does not work right now.

    Lou Braun
  4. XLS

    XLS LawnSite Silver Member
    Messages: 2,038

    I have had the exact situation on a gravely 2760HD and after all the changing out of fuses I replaced the switch .... 3 weeks later ,no fuses shot the system died , fuse was good and I assumed a relay went bad . I replaced the relay which had a pin hole in the top and the system ran a good week and died again . I got POed and just bough the clutch and 4 weeks with out an issue I assume it was that the clutch was bad the whole time causing all the little isses . The machine started acting up when the hours were in the 500s and now it reads 800 and is fixed .
  5. AlohaMowing

    AlohaMowing LawnSite Member
    Messages: 58

    Thanks, all. A new clutch should be delivered in a couple days. I'll report results.

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