New PTO Switch in Scag STHM

Discussion in 'Mechanic and Repair' started by mpm32, Aug 24, 2010.

  1. mpm32

    mpm32 LawnSite Member
    Messages: 58


    I have a Scag STHM from around 2000. Recently the PTO switch was not working when I went to engage the blades. To get through mowing my lawn I cut the sides off the switch off to get at the contacts. I could tell that some of the contacts were bent. I bent them back so they would make contact.

    It got me through the lawn. However, when I disengaged the switch, my amp meter was reading past 10+.

    I got a new PTO switch from the Scag dealer and just installed it. When I engage the blades, the amp meter goes past 10+. When disengaged, the needle goes to all the way to the left to 10-.

    I don't think it's an overcharging situation but I don't know what's causing it and I don't know where to start diagnosing.

    Any thoughts?

    Thanks in advance.
  2. Restrorob

    Restrorob LawnSite Fanatic
    Messages: 11,029

    I would disregard the machine gauge and put a multimeter set on DC volts across the battery and see exactly what the charging system is doing, Check at full throttle with the blades off then with the blades on.

    Anything between 13 and 14.5 volts depending on battery condition would be considered normal.
  3. mpm32

    mpm32 LawnSite Member
    Messages: 58

    Thanks for the quick reply Rob, you helped me once in the past. I'll check that next.

    It does seem like the gauge went bad. Maybe I shorted something with my temp fix of the bad PTO switch
  4. mpm32

    mpm32 LawnSite Member
    Messages: 58

    Turned out to be the electric clutch. Replaced that and all is good.

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