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Scag WB - Blades don't engage.... sometimes

Discussion in 'Mechanic and Repair' started by A1 Grass, Feb 17, 2003.

  1. A1 Grass

    A1 Grass LawnSite Senior Member
    Messages: 330

    I have a Scag SW32. It has a 6-pole switch that engages the blades. The switch looks to be in good shape but occasionally the blades don't engage when I flip it on. It usually happens after running for a 1/2 hour or so - nice and hot. It never disengages when in use. Also, every once in a while a little jolt will kick it on. The blade-clutch is not loose, the bolt that holds it is on tight.

    I am going to clean the contacts on the switch, but they look to be ok as I said.

    Any other thoughts or ideas would help.

  2. xpnd

    xpnd LawnSite Senior Member
    Messages: 378

    Three other areas to add to the check list. Carefully check the wires from the plug to the clutch. These control wires have a habit of becoming frayed/breaking. Once the wires break where they enter the clutch, it (the clutch) is junk even though it is still good. I'm still trying to figure out how to gain access to the wires inside(when they don't break outside far enough to make a splice) and then reassemble the clutch back to working order. Second, check all the connectors. They do not seem to be UV resistant. After several years they crack and can begin to cause intermitent shorts on the frame. If this is the problem, you can go to Radio Shack and purchase new connectors to replace the cracked ones. Much cheaper than buying a new wiring harness. Lastly, if everything checks out okay, put a voltmeter on the engine side of the clutch plug. It should read between 12-13 volts. THis will require a second person since someone will need to be at the handles keeping the OPC engaged, tranny in neutral and clutch engaged while you check the voltage. If not then then there is likely a problem with the capicitor (little round thing) or the voltage regulator(the rectangular black thing attached to the base to the right of the tranny) Or vice-versa. I don't know my way around with electrical things, but when I wasn't getting the proper voltage at the clutch it was the regulator) If you getting a constant 12-13 volts at the plug, then the clutch is probably going bad and is showing up as an intermitent failure.
  3. A1 Grass

    A1 Grass LawnSite Senior Member
    Messages: 330



    I will certainly check all of these out. I really appreciate your more-than-thorough answer.

    I like to do all of my own maintenance when possible, because how can you properly care for something if you don't even know how it works?.... oh yeah, plus I'M CHEAP ... heh heh
  4. ducky1

    ducky1 LawnSite Senior Member
    Messages: 252

    I'm still trying to figure out how to gain access to the wires inside(when they don't break outside far enough to make a splice)

    If you do let me know. I have dug down and done it but they broke again soon due to being shaved thin from the digging.
  5. superstfn

    superstfn LawnSite Member
    from ohio
    Messages: 1

    Also try to check th pto clutch gap adjustment, the clutch has three windows where you can insert a feeler gauge, the gauge thickness to use is .012-.014 turn the three nuts with the springs to EVENLY!! adjust the gap. If the gap is too wide the magnetic force of the clutch cannot hold it especially when hot!!
  6. SWD

    SWD LawnSite Senior Member
    Messages: 988

    Some good answers - however, I believe your intermittent problem to be associated with the wiring harness connection - not the clutch.
    I have spoken with Scag about my 36"wb doing the same thing.
    The response - check the main connection in the wiring harness
    where it all snaps together - look for evidence of a grounded wire or carbon tracing.
    Apparently Scag uses smaller gauge wires in their wiring harness which cannot hold up to the heat and current load which then causes the blades to intermittently engage/disengage.
    My fix was the cut out the factory plug, heat shrink better insulation on the wires, and solder the connections together.
    I have no more problems - even in sustained operation above 100*F
  7. bob

    bob LawnSite Platinum Member
    from DE
    Messages: 4,260

    How many hours are on the clutch? My Grasshopper was acting up sort of the same way. After it was hot, the clutch didn't want to engage. I'd let the mower sit and cool down. I'd even get the backpack blower and help get it cooled. After a while you relize its too far gone , and a new clutch had to be installed. I like the manual clutches that DC's use. Great idea!
  8. xpnd

    xpnd LawnSite Senior Member
    Messages: 378

    Scagg has intentionally engineered a failure in its clutch. The wires will break off at the clutch long before it goes bad. lol. All they have to do to fix this problem is make it a recessed spade connector on the clutch
  9. 65hoss

    65hoss LawnSite Fanatic
    Messages: 6,360

    My lazer had the same problem last year. It would sometimes start the blades, sometimes it wouldn't. I took the switch out and decided to take it apart. It was melting inside. I replaced the switch, and it has been perfect since. By the way, it is a cheap part.
  10. kickin sum grass

    kickin sum grass LawnSite Senior Member
    Messages: 628

    I was surprised to see so many people having trouble with the wiring break.
    in my experience it has always been the pto adjustment when the thing won't start or only sometimes when it is hot. Usually just make an adjustment and you are good to go. If the cluch is really old than you may have to replace it. We always check the adjustment 2x year and since we started doing this we have not had 1 problem with a pto clutch except for on an exmark rider which has no adjustment capablities.
    just my experiences but i will look out for the wiring issue next time we have a problem.

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