M59 Help: Dealer Wants $6K to Replace the Wiring Harness

[TheParkRanger]

Kubota M59, unknown year, ~2600 hours. I've had it about 10 months, have close to $40K into it including major service, new brakes, and completely rebuilt loader and loader hydraulics. I just point this out to say I've been operating with an open checkbook to get this puppy sorted, but I'm pretty sure the dealer is tired of fussing with it and finally gave me a go-away quote regarding this electrical gremlin I've been chasing.

Unfortunately, tractor has been more down than up. I'm the official-unofficial mechanic here at a tropical fruit park under construction in Central Florida. Primary duties for this bad boy are moving mulch, logs, and general sitework. We're blessed to have it, but electrical issues have hobbled it a lot.

TL;DR - Machine keeps blowing:
- the (#7) 5amp fuse for the "brake lamp switch" (orange, 2nd from top right)
- the 30amp slow-blow "keystop" (pink, 2nd from left)

Despite their labeling, one or both of them are involved with the start sequence, specifically the fuel shutoff solenoid (which I have replaced).

Trouble Sequence: No Start
- When turning the key to the 2nd position (before start) — the operator is supposed to hear to the fuel shutoff solenoid open (it does not)
- Then as soon as I depress the clutch pedal (again, before start), the #7 5amp will blow

- The 30amp slowblow gives me trouble in fits, I can't replicate a specific sequence before it

Attempted Remedies
- (3) trips to the dealer where they replaced the fuses, drove it around a little bit, sent it home to me, had the fuses continually blow again 1-3hrs back into operation
- 4-5 hours (from me) looking for any broken wires that I could see in these circuit(s), replacing, repairing, and protecting them ( I can solder pretty alright)

Would be looking for any and all help — including moral support — in chasing down these electrical gremlins, suggestions for things to do beyond above, tips for finding breaks I can't easily see, or ideas on how to bypass some of the circuit to help troubleshoot. I have a multi-meter but I'm not super great with it, for example, I'm not even sure if a fuse is blowing if that intones a problem upstream or downstream of the fuse, or if it could be both.

Thanks in advance. I need you guys.

 

[KWentling]

You are only looking down stream (load side) of the fuse. A good method for finding shorts is to substitute a test light in place of the fuse, and watch the light as you wiggle the wiring. You can make a test light out of automotive bulbs. Say a headlight bulb for the higher amperage fuse and a taillight bulb for the lower amp fuse.

 

[Oz_Kioti]

This might be totally irrelevant, however, for what it's worth:

A mate's Vermeer SkidSteer working on our place, suddenly wouldn't start. After much probing and part-dismantling to get at the fuse next to the starter motor, we had a closer look at the accessible 4-fuse block next to the battery, removing the fuses one by one. We found the problem:

Rather than replacing the fuse block, we fitted an external fuse holder and problem solved:

Connectors carrying decent current are potential sources of grief. I have a Braumeister 50 beer-making machine, which has two heating elements - a 1.3Kw and a 2.0Kw - connected to the main control box with fancy German-made locked-in-place connectors. BUT, good as they are, one of those went dodgy, with the tell-tale signs of arcing and getting very hot. Replacement connectors and sockets on their way.

 

[TheParkRanger]

Thanks for your quick replies, OZ and KW.

I forgot to ask a pointed question:

Where is/what is the "stop lamp" so I can start from that load and work back to the fuse block. I'm confused by both the manual and the diagram, if that's the parking brake lamp or the brake lights (wait, does this tractor have brake lights) or something related to the light on the instrument panel?

 

[anomad]

Stop lamp is usually what we call a brake light here in the States. I'd take a good look at those up on the canopy first. I've had a lot of japanese cars and equipment.

And not troubleshooting specifically, but can you spend 45 minutes with a pressure washer on it? That would make working on the dirty girl a little easier and maybe totally not happening on your job site... LOL

Edit: I had an old Isuzu in high school that would blow fuses if you had something like a bad license plate light bulb. Maybe check all the light bulbs and eliminate that variable.

 

[Oz_Kioti]

I just printed out the circuit on an A3 size sheet (for clarity) to see what the link was with the clutch pedal blowing that fuse when pressed.

I'm not a sparkie, but comparing what needs to happen in my Kioti, I'm assuming:

The 'Key Switch' sends power via a 5amp fuse to: the PTO switch, the clutch pedal switch, the seat switch, and the seat turn switch.​

​

Each of these switches sends power to the ECU if conditions are met - ie the PTO is OFF, the clutch pedal is pressed, there's weight on the seat, etc. Then the ECU says OK - fine to engage the starter.​

So my first thought is to check for a short in the clutch pedal switch, which would prevent the ECU getting the GO signal, AND blow a fuse as well.

I'll next look at the brake light fuse issue. That's a strange one! However I have also had weird things happen with dodgy light bulb connections, so yeah, check all those!

 

[KWentling]

There also may be other pages in the electrical with more detail on specific systems, such as lights.

 

[TheParkRanger]

LOL anomad, yeah she's pretty soiled, I gave it a quick garden hose down in the morning twilight, power wash definitely needed.

Okay well here's a update:

- We're back in the barn (yeah)
- I disconnected the brake lights — 5amp fuse still blew on key turn to start (one click later)
- so I thought... what if I just tryyyy to start without the 5amp fuse in at all and... IT STARTED

Which means?
- an open circuit is better than a broken circuit?

Isn't a broken fuse the same as having no fuse? How does that make sense?

I'm super scratching my head at this one.

Also not completely scientific in that I temporarily have a 40amp slow blow in the 30amp spot since I was down to my last 30amp. I think I've gone through 50-60 fuses total of both types in trying to hunt down this gremlin. Time to reorder some of those so I can tech this in the barn where all my tools are.

I'm still not sure how the 30amp and 5amp are related (anyone able to follow that trail on the wiring diagram?)

I appreciate all the responses, guys. Thank you KW, OZ, and anomad for talking this out. I've been here before, so I know it's not yet licked. I'll keep updating since I hate dead threads where the outcome is unknown.

 

[Hay Dude]

Does this model Kubota have a PCM (a computer box)?
I had 2 different Kubotas that had PCMs that went bad.
Symptoms included constantly blown fuses and complete loss of certain electrical functions. PCM replacement was quoted at about $5,000 for one of my Kubotas.

 

[KWentling]

LOL anomad, yeah she's pretty soiled, I gave it a quick garden hose down in the morning twilight, power wash definitely needed.

Okay well here's a update:

- We're back in the barn (yeah)
- I disconnected the brake lights — 5amp fuse still blew on key turn to start (one click later)
- so I thought... what if I just tryyyy to start without the 5amp fuse in at all and... IT STARTED

Which means?
- an open circuit is better than a broken circuit?

Isn't a broken fuse the same as having no fuse? How does that make sense?

I'm super scratching my head at this one.

Also not completely scientific in that I temporarily have a 40amp slow blow in the 30amp spot since I was down to my last 30amp. I think I've gone through 50-60 fuses total of both types in trying to hunt down this gremlin. Time to reorder some of those so I can tech this in the barn where all my tools are.

I'm still not sure how the 30amp and 5amp are related (anyone able to follow that trail on the wiring diagram?)

I appreciate all the responses, guys. Thank you KW, OZ, and anomad for talking this out. I've been here before, so I know it's not yet licked. I'll keep updating since I hate dead threads where the outcome is unknown.

I urge you to set up a test light to replace the fuse. It's the way the pros find shorts. Easy to do. No more feeding it fuses. The light is current limiting so no danger to the wiring. Easiest is to find an old headlight or taillight assembly and rob the bulb socket and some harness. Connect a length of wire to it with appropriate spades to plug into the fuse holder. Use enough wire so you can get the bulb up where you can see it. If you have an amp clamp you can monitor the amperage too to know what load (normal verses dead short) you are seeing. Changing light brightness when wiggling wiring (or pushing the clutch pedal, etc.) is what you are looking for.