Kubota z723KH safety switch or electrical issue

[Eric502]

New here, been active over on another site for a while. Got an interesting issue and was encouraged to try my efforts over here as well. I am always open to ideas, especially electrical ones. Cause I am not great at it.
Here is the initial deal:
This mower was bought in 2015 and has under 300 hours today, so it is not used a lot. So far this season when I have used the mower, it has performed as expected. Then it developed this issue where I could be operating the mower and it would shut down, like you turned the switch off. I can restart the mower, it will run perfect. It does not have anything hindering restarting the mower after it dies. Release the parking brake-dies. Engage the PTO with the parking brake on, while engine running in park/neutral-dies. In these two conditions the mower should continue to run without turning off.

I am looking for suggestions cause I am running out of ideas. I have replaced the following really cause I was just trying to see if it changed the scenario. So far, none of these changes have resolved this situation:

4 automotive like CIT Relay A2F1CSQ relays-replaced.
all blade fuses tested, slow blow 30amp tested for insanity purposes
Ignition switch-replaced
PTO switch-replaced
Kubota time delay switch-replaced (NOT CHEAP) (delays safety deactivation of engine due to operator bouncing in the seat etc)
seat safety switch-replaced
Parking brake switch-replaced

I have something somehow tied to the PTO and the parking brake that is stopping this machine from operating. I am down to tracing wires unless someone has an idea.

Today: mower will start and run perfect. You cannot move the machine or operate it in any other manner than this. Start it, remove parking brake-dies. Restart it, leave the brake on while sitting in the seat, sticks in neutral... engage PTO, the machine will die. (should run with blades going while sitting in neutral park.)

I will reply to this with what I have done since this initial finding.

 

[Eric502]

As a followup.... the above began a couple weeks ago. And while yes, I threw some parts at as you can see above for a Hail Mary... I did try to be logical in how I did so, or at least I thought I was being logical in the way I did it. No resolutions.

SO... I do not have a WSM or a diagram of this stuff. Tempted, and they are very valuable and good to have. But I have taken it upon myself to go the harder route I suppose and chart this stuff the best I can as I have been going through the ENTIRE harness testing continuity and looking for a short or bad ground. SO far as of today... NOTHING. I am seriously wondering this was not a situation where a spade connection or the like was faulty and (essentially) I have gone further down a rabbit hole than I perhaps needed. Regardless.... I have all this junk out, disconnected, easy(er) to get to... and so since I have seen nothing I am looking to those that have better luck with this stuff to see if they have some suggestions. It is likely right in front of me and I would not see it. I am attaching a diagram that I have made myself as I have tested and traced wires. So, yeah... I'm not afraid to put in the work.

Also since the initial failure:

1. Grounds to starter are cleaned/tested
2. Battery terminals are always cleaned-battery is old though. Shows 12.7V sitting.
3. Starter positive wires were NASTY. Protective boot captured water and stuff was bad. Cleaned all that off, brushed is all with a wire brush, tapped the connections to ensure clean, added copper ant seize and reinstalled.
4. And if there is a connection... if I have had it apart, dialectic grease gets used putting it back.

 

[Eric502]

Well, one gentleman suggested that they had the "same symptoms" and had to end up replacing the harness on each mower to resolve the issue. He did not elaborate on the nature of their symptoms. Said his dealer told him that they keep a few close by due to this. IDK, could be. Heck if no other ideas and no solution then I am certainly headed that direction so it seems.

Before I do that, I will try to hook things back the best I can without having to fully wrap and tie it all up and give it a go. Just in the off chance that I did find something and just don't know it, like a connection faulty due to whatever reason.

I will say this, I do not see where the wiring in this harness is faulty, overly exposed to elements, or anything. It is far from what one cold say is a "cheap" wiring harness. Looks real good and sealed up. Worst thing I have seen was the + on the starter corroded due to the protective boot capturing water. That could happen to anything.

 

[Darryl G]

Gremlins are very sneaky and cannot usually be seen, even by those who are very familiar with their habits.

These safety interlock systems can be infuriating and difficult to diagnose. I've looked at several used machines with them defeated. No, I didn't buy them.

Good luck!

 

[bertsmobile1]

The interlock switches are cheap & nasty
They corrode internally and errode where the plunger rubs most often .
Then there is wear in the mower itself which can mean the levers do not depress the plungers far enough to make / break contact so I put a self tapper into the plunger to make it longer
SO I always test switches in place not in my hand
My usual method to work through these sorts of problems is to bypass the actual switch with a short jumper at the plug , one at a time till the problem goes away
The last one you jumped is the problem
For mowers full of relays like yours I jump the relay using the same short jumpers ( 30 to 87a ) .
If this fails then I use longer jumpers to go from one plug to the next thus bypassing the loom
With old mowers you get corrosion at the terminals and on the terminals and between the terminal & the wire.
Add to that unsupported crimps can fracture at the crimp and then make & break contact creating a random problem near impossible to diagnose by any means other than bypassing the loom .
I am not familiar with this mower & do not have a wiring diagram for it so the above is generic but it is how I have been sorting out electrical problems for the past 11 years and have not been beaten yet , sent sark raving mad yes but beaten no .

 

[Eric502]

@bertsmobile1 you have a lot of helpful suggestions there. Another gentleman has given me some as well that seems to have done this a few 20 times or so. Me... not afraid to work on stuff, but I am not a big electrical go to person at all. So basic steps that help rule things out in a process is very helpful. Thank you. The one statement here.... wow, never would have thought of this; "Then there is wear in the mower itself which can mean the levers do not depress the plungers far enough to make / break contact so I put a self tapper into the plunger to make it longer"

I have to circle back to this project, busy like many of us all are. It will take me some time to do this appropriately as persons like yourself have suggested. I will be watching the threads for other ideas and will update as I work though all of this. I always appreciate any ideas. Thank you all.

 

[bertsmobile1]

Electrickity is really simple if you just remember that everything has to go in a full circle from the battery + all the way back to the battery -
In reality it is the opposite way round but + to - resonates with most peoples logic and it really does not matter just as long as the loop is complete
So you break every problem down into individual circuits and ignore the rest
So for cranking you have battery + -> solenoid -> fuse B terminal on key switch -> S terminal -> PTO switch -> brake switch -> starter solenoid -> battery -( via frame )
The kill circuits are the same except the frame replaces the battery
Frame -> seat switch -> parking brake -> magneto -> frame
And of course you want this circle to be incomplete so one of the switches has to be open or the circuit is closed and there will be no spark .

People get hung up on the fact that you can switch the + side or the - side with DC it makes no difference and - switching seems to confuse people .

 

[Darryl G]

The interlock switches are cheap & nasty
They corrode internally and errode where the plunger rubs most often .
Then there is wear in the mower itself which can mean the levers do not depress the plungers far enough to make / break contact so I put a self tapper into the plunger to make it longer
SO I always test switches in place not in my hand
My usual method to work through these sorts of problems is to bypass the actual switch with a short jumper at the plug , one at a time till the problem goes away
The last one you jumped is the problem
For mowers full of relays like yours I jump the relay using the same short jumpers ( 30 to 87a ) .
If this fails then I use longer jumpers to go from one plug to the next thus bypassing the loom
With old mowers you get corrosion at the terminals and on the terminals and between the terminal & the wire.
Add to that unsupported crimps can fracture at the crimp and then make & break contact creating a random problem near impossible to diagnose by any means other than bypassing the loom .
I am not familiar with this mower & do not have a wiring diagram for it so the above is generic but it is how I have been sorting out electrical problems for the past 11 years and have not been beaten yet , sent sark raving mad yes but beaten no .

Good advice regarding testing switches in place. I've had switches that weren't getting depressed enough. Even switch mounting brackets can bend over time causing it to not depress the plunger sufficiently.

 

[lugbolt]

if you get up out of the seat, park brake on, pto OFF, and engine dies you may have a brake switch issue. IIRC the brake switch on these is a NO/NC switch. 4 contacts. 2 are normally closed (NC), the other two normally off (NO). Activating the plunger turns the NO switch to a closed circuit, and the NC switch to an open circuit. If one side of the switch dies it'll start just fine but when you get outta the seat, it'll kill spark.

The seat switch is probably workin if the engine drops spark when you get up outta the seat.

Possible (though not really likely) that PTO switch is failing as well. Jiggle it a few times before you jump out of the seat and see if jiggling the PTO switch changes anything. Same for the brake switch. Move the brake on and off a few times while getting out of the seat kinda at the same time.

 

[boatmoter]

New here, been active over on another site for a while. Got an interesting issue and was encouraged to try my efforts over here as well. I am always open to ideas, especially electrical ones. Cause I am not great at it.
Here is the initial deal:
This mower was bought in 2015 and has under 300 hours today, so it is not used a lot. So far this season when I have used the mower, it has performed as expected. Then it developed this issue where I could be operating the mower and it would shut down, like you turned the switch off. I can restart the mower, it will run perfect. It does not have anything hindering restarting the mower after it dies. Release the parking brake-dies. Engage the PTO with the parking brake on, while engine running in park/neutral-dies. In these two conditions the mower should continue to run without turning off.

I am looking for suggestions cause I am running out of ideas. I have replaced the following really cause I was just trying to see if it changed the scenario. So far, none of these changes have resolved this situation:

4 automotive like CIT Relay A2F1CSQ relays-replaced.
all blade fuses tested, slow blow 30amp tested for insanity purposes
Ignition switch-replaced
PTO switch-replaced
Kubota time delay switch-replaced (NOT CHEAP) (delays safety deactivation of engine due to operator bouncing in the seat etc)
seat safety switch-replaced
Parking brake switch-replaced

I have something somehow tied to the PTO and the parking brake that is stopping this machine from operating. I am down to tracing wires unless someone has an idea.

Today: mower will start and run perfect. You cannot move the machine or operate it in any other manner than this. Start it, remove parking brake-dies. Restart it, leave the brake on while sitting in the seat, sticks in neutral... engage PTO, the machine will die. (should run with blades going while sitting in neutral park.)

I will reply to this with what I have done since this initial finding.

almost sounds like a weak ground all those circuits are sharing