Scag start problem

[Proud Veteran]

Question! I have a Scag 48" Tiger Cat II with the 22hp Kawasaki engine. Key does nothing so I tried jumping straight to starter. Started right up so next I thought solenoid. I noticed in the wiring diagram that there is a diode in the wire going from the ignition to the solenoid so I ran a wire from the ignition to the + side of the solinoid. Starts just fine! Sure enough there is no continuity from the key to the solenoid so I suspect the diode is bad. I was an electronic specialist in another life so I know that a diode let's current flow one way but not in the other. My question is this, what is the risk of bypassing the diode and just running a wire from the ignition switch to the solenoid and if it will cause damage anyone know the location of this diode? Any feedback is greatly appreciated!

 

[LittleBill21]

are you sure the diode isn't across the coil terminals of the solenoid?

 

[RandyT]

There are a lot of components between the key switch and solenoid. Namely the pto switch, seat switch, parking brake switch, the brain box that controls everything to name a few.

 

[ddbackhoe]

Question! I have a Scag 48" Tiger Cat II with the 22hp Kawasaki engine. Key does nothing so I tried jumping straight to starter. Started right up so next I thought solenoid. I noticed in the wiring diagram that there is a diode in the wire going from the ignition to the solenoid so I ran a wire from the ignition to the + side of the solinoid. Starts just fine! Sure enough there is no continuity from the key to the solenoid so I suspect the diode is bad. I was an electronic specialist in another life so I know that a diode let's current flow one way but not in the other. My question is this, what is the risk of bypassing the diode and just running a wire from the ignition switch to the solenoid and if it will cause damage anyone know the location of this diode? Any feedback is greatly appreciated!

green wire and green with black stripe? Is the diode across the relay coils. It would be best to replace the diode, its job is to help keep the relay from burning out when it switches legs.

 

[LD1]

If I am looking at the same schematic as you......looks like your mower has a "module" or little brain-box thing.

Looks like that diode protects that brainbox from the voltage spike when the starter solenoid field collapses.

If thats the case....I'd either test and/or replace just that diode. Most cheap volt-meters will test diodes.

But RandyT's statement of alot of components between the key and starter.....yes and no.

Its NOT like a continuous series circuit daisy-chaining through all the safetys and if any single one is open it wont start.

All the safety switches go through that little brain-box. And if the brain-box gives the "all-clear" to start, it gives the ground for the start relay on the green and black wire. The relay then gives the start solenoid 12v on the green and white wire.

Thats my amateur diagnosis.

And as cheap as manufactures are anymore....I would find it unlikely for them to put something there (diode) that wasnt actually needed.

 

[WinterDeere]

Classic "flyback diode", essentially a surge suppressor, as LD1 suggests. If bad, just replace with similar type and size. DigiKey is your friend, they do small credit card orders for personal stuff. Heck, you can probably get them on Amazon now, too.

Where's the schematic you guys are looking at?

<-- MSEE

 

[EddieWalker]

I bought my Scag Wildcat new from the dealer back in 2012 with the 26 HP Kawasaki engine. For the first couple of years, it was flawless. Then I started having issues getting it to start. It was always a safety switch that needed replacing. I had to check all of them, and then bypass it, or replace it. This became a common issue, but then the PTO switch quit working, and then I had to replace the generator, twice. I also replace the PTO switch 3 times.

When it was about 5 years old, I never expected it to start. There was always an issue that I had to fix, bypass, or replace. It might work the next week, or even a couple weeks in a row, but never a full month. Then it started blowing the 20 amp fuses. It would run for an hour, maybe two hours, or maybe half an hour, then the PTO would stop working and I would replace the fuse. I could go through 3 or 4 fuses in a day.

Three years ago I had enough. I pulled every wire out of it and I bought a new aftermarket key switch, and a heavy duty toggle switch for the PTO. I ran the bare minimum for wiring. Just what I needed to get it to start, turn off, charge the battery, and run the mower blades. Since then, it's worked perfectly every time I use it!!!!!

 

[WinterDeere]

Three years ago I had enough. I pulled every wire out of it and... Since then, it's worked perfectly every time I use it!!!!!

Was Scag ever owned by Lucas Electronics? Sounds like a 1970's British sports car, in terms of electrical system reliability.

 

[LD1]

Classic "flyback diode", essentially a surge suppressor, as LD1 suggests. If bad, just replace with similar type and size. DigiKey is your friend, they do small credit card orders for personal stuff. Heck, you can probably get them on Amazon now, too.

Where's the schematic you guys are looking at?

<-- MSEE

 

[EddieWalker]

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.