Scag start problem

[LD1]

I've been sharing my issues with my Scag mower for awhile now, and from what I've heard from others with different brands of zero turns, it sounds like everyone has issues with their electrical systems.

Yup....it's not just scag.

The wildcat is a commercial grade mower (I have one too but with the Kohler 27 or 28hp).

But comparing exmark, toro, scag, hustler, etc.....they are pretty much all identical except paint color.

They use the same generic key switches, same safeties, pto switch, etc etc.

Engine options, hydraulics, etc....pretty much all the same.

Deck designs (spindles and airflow) are really the only differences other than paint color.

I do work on a lot of different mowers for my buddies landscape company. My wildcat is actually one of their older mowers I bought. But they have scag walk behind, scag v-rides, toro 6000-series, toro grandstands, exmark walk behind, exmark riders, throw in an odd JD z700 series and a older Kubota.

You'd be surprised just how many of these smaller components are interchangeable. Pretty much all the switches, and even pto clutches for the most part.

On my personal scag.....I bypassed ALL the safeties. Which is the seat switch, park brake, and both levers "home" position.

Means I can get off the mower to move a stick without it dying because I forgot something or didn't get one of the levers home.

The ONLY issues I have is when a fuse blows. It's usually for the charge. No rhyme or reason to why it blows. Maybe once a year. But I don't notice it til the mower either quits (battery runs dead) while mowing and it won't restart....or if I am lucky to finish that mowing but have a dead battery next time I try and mow.

 

[WinterDeere]

I've been sharing my issues with my Scag mower for awhile now, and from what I've heard from others with different brands of zero turns, it sounds like everyone has issues with their electrical systems.

The only issue I've ever had with my 2007 Deere Z757 ZTrak is a seat switch delay module relay that went bad ca.2020. It was intermittent, which means I had to let it "fail" two or three times before confirming the issue, but the repair was ultimately as easy as unplugging the old one and plugging in a new one.

I also had two PTO clutch failures, before noticing a small but hidden hole in the muffler, that was directing a jet of hot air right at the clutch coil, ultimately causing them to overheat and fail. I can't blame the electronics for that, but I do wish they had done a better job of welding that muffler, as the hole was the result of a failed heat shield weld.

 

[WinterDeere]

[wiring diagram]

Thanks. Unfortunately, it's hard for someone not already familiar with these mowers to get much from that wiring diagram, if you don't already know the components at each end. I have no idea what's on the other end of "module plug", and that would be required to figure out the pin-out of "relay", and thus what that diode at the engine adapter harness plug is actually doing.

The reversed 600V/2A diode at the clutch is a classic example of a flyback diode, reversed biased and there just to absorb a transient when the clutch is disengaged. But I assume the one in question is the one at the engine adapter harness, and its function is less obvious from the wiring diagram alone. I'd guess LD1 is right though, it's for protection of the engine module electronics.

 

[LD1]

Thanks. Unfortunately, it's hard for someone not already familiar with these mowers to get much from that wiring diagram, if you don't already know the components at each end. I have no idea what's on the other end of "module plug", and that would be required to figure out the pin-out of "relay", and thus what that diode at the engine adapter harness plug is actually doing.

The reversed 600V/2A diode at the clutch is a classic example of a flyback diode, reversed biased and there just to absorb a transient when the clutch is disengaged. But I assume the one in question is the one at the engine adapter harness, and its function is less obvious from the wiring diagram alone. I'd guess LD1 is right though, it's for protection of the engine module electronics.

The other side of the "module" plug is just that....and electronic module.

Electronic Module

www.scagparts.net

However, it has nothing to do with the engine, and isnt an "engine" module at all. Rather it is a safety interlock module. All the safety circuits go through it (instead of daisy-chain fashion). And if all safety's are in their proper position, it will give the ground signal to the start-relay.

IT also has some kind of "logic" to it. Meaning if blades are ON and seat becomes unoccupied, it kills the mower and deck. OR if park brake is set, but handles come off home position.....also kills the engine. Or as long as park brake is set, handles in "home" and PTO is off.....it ignores the seat switch (meaning you can get off without killing engine.

Again, its got a "logic" base to it. And being that its a printed circuit board....my best guess is the diode is preventing a voltage spike on that board when the starter solenoid is de-energized