riding lawnmower interlock system

Discussion in 'Off-Topic' started by electronis whiz, Aug 13, 2011.

  1. electronis whiz

    Thread Starter Well-Known Member

    Jul 29, 2010
    519
    27
    i have started having problems with our riding mower. unless the blades are on it will run like it has air bubles in the line. due to the blades being on and it seems ok. i believe it to be a defective switch somwhere.
    there is 1 NO switch on the parking break, 1 NC on the seat, 1 on the clutch i beleve is NO but not certian, and the blade apears to have a dpst.
    there is also a special ignition switch that in order to mow in reverse the key had to be turned then a button pressed. this made an led come on and alowed mowing in reverse (else it would die). however after about 1.5 years that position on the ignition became defective so i disconected a metal plate that touched the shift lever and grounded it when in reverse. (then it worked normaly both ways)

    the switch on the parking break is closed when brak is aplied somehow this works with the seat switch and keeps it running only if the break is on. (then you can get off.)

    there are no schematics on the electrical system avalible and there are many duplicate colored wires in the system. i was hoping somebody may have an idea on how this system works. the switch on the parking break is closed when brak is aplied somehow this works with the seat switch and keeps it running only if the break is on. (then you can get off.)
     
  2. electronis whiz

    Thread Starter Well-Known Member

    Jul 29, 2010
    519
    27
    if it helps i also found this

    headlights,________1 green (goes to ignition switch) & 1 blue (goes to headlight switch).
    light switch,_______1 blue (goes to headlight) & 1 white (goes to engine)
    seat switch,_______1 yellow/white(goes to brake/clutch switch)
    & 1 yellow/black(goes to deck switch)
    deck switch,______1 orange/white (goes to starter relay) 1 yellow(goes to
    brake/clutch switch). 1 orange/black(goes to brake switch) 2 yellow/blacks 1 (goes to seat switch) the other goes to a connector with a yellow wire?
    ignition switch,____2 green wires 1(goes to ground) (the other goes to headlights)
    starter relay,______2 battery cables 1(goes to + side of battery) other
    goes to starter. 1 red wire goes from positive side of relay to 20 am fuse. 1 orange/white wire (goes to deck switch)
    20a. fuse holder,___1 red(goes to + side of starter relay. 1 red/white (goes to ignition switch)
    brake/clutch switch, 1 orange(goes to ignition switch) 1 orange/black(goes
    to deck switch) 1 yellow/white( goes to seat switch)
    2 yellows, 1 (goes to the engine) other (goes to the deck switch).
    engine,___________ 1 red/black(goes to ignition) 1 white (goes to light switch) 1 yellow (goes to deck switch)

    it starts so to me it seems like it would have to be the break switch that conects to the deak switch. if ther deck switch was bad it shouldnn't even turn over. unless the other pole is bad but i have never hared of only 1 pole failing in a multi pole switch.

    whitch do you switch do you think i should investigate?
     
  3. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,157
    Have you located the service manual for your model?
     
  4. electronis whiz

    Thread Starter Well-Known Member

    Jul 29, 2010
    519
    27
    the service manual is not avalible
     
  5. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,770
    929
    The most likely point on the engine to 'kill' it would be the spark. Either at the coil or at the plug. The interlock system most likely works by grounding the spark and thereby quickly stopping the mower. Investigate from the plug(s) backwards.
     
  6. debe

    Well-Known Member

    Sep 21, 2010
    946
    184
    Ive had plenty of multi pole switces have one that is faulty.
     
  7. mbohuntr

    Active Member

    Apr 6, 2009
    413
    32
    It sounds like a Cub Cadet...:( I have not torn one apart... yet...:rolleyes: , but I would think you could narrow the search to only those switches that would interface with the blades. The two position key switch w/ led, the seat, and possibly the hydrostatic pedal. Look for loose/bared wires. Try a call to your dealers service man who might see this bad switch a lot.
     
  8. Pencil

    Active Member

    Dec 8, 2009
    271
    38
    When the engine is under load (blades on) engine runs smoothly.

    When engine is not under load (blades off) engine RPM does not
    stay constant. The engine revs up then down, up then down.

    Is this correct?

    Basically:
    1. governor opens throttle, RPM increases,
    2. governor closes throttle RPM drops,
    3. governor opens throttle, RPM increases,
    4. Repeat from step 2.

    If this is correct you may need to check carburetor and the mechanical
    portion of the "governor".

    It will be much easier if it is an electrical problem. A lot of "newer"
    lawnmowers do this as they age due to the changes in the carburetor
    and other things related to emissions standards and "more cost effective"
    manufacturing. I am not an expert, only an observer of this particular
    problem on many occasions.

    This time I hope I am wrong.
     
  9. debe

    Well-Known Member

    Sep 21, 2010
    946
    184
    If its eratic engine RPM under no load , sounds more like fuel feed or carby problem, not electronic at all.
     
  10. mbohuntr

    Active Member

    Apr 6, 2009
    413
    32
    I re-read your origional post , I misunderstood it, I thought it ran badly when it was under load. My bad. I agree with the carb/ governor posts. I would take it in to have it checked for bad springs (little ones) plugged ports, or maybe the fuel filter.
     
  11. Pencil

    Active Member

    Dec 8, 2009
    271
    38
    I suggest a microcontroller to monitor engine RPM using a hall
    effect sensor. Output to a throttle control selenoid
    to keep RPM constant regardless of load condition.

    Now its an electrical problem.:D:eek::p

    Problem solved?

    Seriously, I have always suspected engine wear decreases intake
    manifold vacuum, which causes the circuit in the carb. that is supposed
    to supply fuel to underperform, this causes RPM to drop. The governor
    then opens the "butterfly" this brings the other circuit into play which
    supplies plenty of fuel, RPM increases.....

    The bottom line is clean carburetor, check integrity of carburetor to
    engine seal, maybe consider a valve job.

    Just guessing.

    Same gaurantee on lawn mower advice as any other.:D
     
    Last edited: Aug 14, 2011
  12. electronis whiz

    Thread Starter Well-Known Member

    Jul 29, 2010
    519
    27
    i have checked the fuel filter and it apears to be ok. but there was a spider in the gas take in the area of the hose to the engine. i cleaned the tank out blew the lines out with air and chacked the air & oil filter they bothe seemed ok. i checked the spark plug it just had some white sut looking stuff on the outside of the terminal. i cleaned it up and it still does it. it sounds like air in the line because it seems to cutout every so often. but the rate of the cutoffs is consistant and changes with the speed.

    i originaly beleved it to be electrical due to the blades SEEM to stop the problem. but they may be aiding like a fly wheel and this somehow is stoping it. it could be doing it with blades on but due to the noise they make i can't hear it, when it would skip the front would kind of shake but i don't see this with blades on either unless there vibration is nutrilizing it.

    i used it aprox 2 weeks before and had no poblem with the engine. but i hit a small aprox thumb size stump it just hit the deck and i shut it off because it was trying to stall. i pushed it off and around the stump and started up agin and had no problem till a little while later it ran out of gas. then i filled it up finished and parked it and left it till the other day when i used it again. i went to start it up it tryed but sounded like the battery was weak i got off opened the hood every thing loked ok. then i got on again and puched the breake turned the key and it turned on it started think there was somthing wrong with the brake switch.
    the mower is a yard machines by MTD from aprox 2005.
     
  13. mbohuntr

    Active Member

    Apr 6, 2009
    413
    32
    You may have dislodged something in the tank/lines that has plugged your ports, could be other things... call the guy..What is your time worth??? Just my 2 cents.
     
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