2013 BX 2370 intermittently blowing the timer/relay fuse. It's highly intermittent.

[BX25D Rookie]

First, I already have the workshop manual. And the wiring diagrams/schematics.
Second, I have several Fluke digital multimeters. And clip leads along with various jumper wires.
Third, I have 20+ years experience as an ASE Master Certified Auto/Light truck technician.
Doing electrical/fuel injection/computer controls diagnostics & repairs professionally.
Fourth, I do all of my repairs and maintenance for all our vehicles here at home.
Fifth, I still have all of my tools from the car/truck days.

The above being said, I am looking for a helping hand where to look for this highly intermittent fuse blowing.
I mowed 97 hours with this machine last year, the fuse popped once on the last mow of the year in October.
Then you can't turn the machine off with the key and have to depress the engine stop solenoid by hand.
I replaced the fuse and the tractor operated as designed for about ten hours.

Yesterday when mowing at the cabin, the timer/relay fuse popped again.
After about four hours continuous mowing.
Today, I replaced the timer/relay fuse again and drove the machine up/down the driveway for about 10 minutes.
Zero problems, the fuse did not blow and all is good again.

For those of you who might work on Kubota BX machines at the dealership level, do you have any suggestions?
What part(s) have you seen that exhibit this highly intermittent behavior?
If I was to go out and test resistances and voltage/amperage right now, everything would test fine.

 

[PaulL]

I'm not a workshop mechanic on these.
But you have no replies, so I'll give one anyway.

Logically it's a short somewhere, or some component flowing more current than it should intermittently (no special thinking needed there).
Short seems more likely, but in concept you could get some sort of feedback or reverse current when a coil releases.

I asked AI some questions to get some hints. And actually, the answer gave some useful things that could be true (or could be AI hallucinations). If nothing else, could be somewhere for you to start looking.


On a 2013 Kubota BX2370, the "Timer Relay" circuit is primarily responsible for controlling the Engine Stop Solenoid.

Kubota uses a "pull-to-kill" setup on these machines. When you turn the key off, the OPC (Operator Presence Control) timer relay sends a high-amperage current to the stop solenoid for roughly 5–10 seconds to physically pull the fuel rack into the shutoff position. Once the time lapses, the current drops to prevent the solenoid from burning out.

Because the problem is highly intermittent (popping after hours of continuous mowing or months apart), standard static multimeter testing will show everything is normal. The issue is almost certainly a dynamic failure caused by heat, vibration, or mechanical movement.

The primary components and failure points that can cause this specific fuse to blow include:

1. The Engine Stop Solenoid (Internal Short)
This is the most common hardware failure on the circuit.

• The Cause: The solenoid has internal copper windings. As the tractor runs for hours, the engine bay gets hot, causing the insulation on these windings to expand. If the insulation is degraded, a "hot short" occurs internally only when the solenoid is energized at high temperatures.
• What to check: Look for physical distortion, swelling, or cracking on the plastic body of the stop solenoid.

2. Wiring Harness Chafe Points (Short to Ground)
Because the fuse blows intermittently while operating, a wire in the harness could be vibrating against a sharp metal edge, momentarily touching bare metal and grounding out.

• The Main Trailing Spot: On the BX series, check the wiring harness branch that runs over the top of the engine bellhousing, near the starter, and down to the stop solenoid. Vibration from mowing can rub the plastic conduit thin.
• The Steering Column/Dash Chafe: Check the harness right where it passes through the firewall or rubs against the steering column mechanism under the dash.

3. The OPC Timer Relay Unit itself
The timer relay is a solid-state module (usually a small black or grey box located under the dash/steering cowl area).

• The Cause: Internal electronic breakdown. Over time, internal capacitors or transistors can break down under sustained thermal load. If it latches internally or suffers a momentary internal short circuit to its own ground pin when cycling, it will instantly pop the fuse.

4. A Binding Fuel Shutoff Linkage

• The Cause: If the mechanical linkage between the stop solenoid and the injection pump fuel rack is sticky, binding, or packed with grass debris, the solenoid has to work incredibly hard.
• The Result: The physical resistance forces the solenoid to draw maximum stalled amperage (locked-rotor amperage) for the entire duration of the timer's countdown. If it draws slightly above the fuse rating because it's mechanically jammed, the fuse will blow.

5. The Ignition Switch or OPC Seat/PTO Safety Switches

• The Cause: The circuit routes back through the safety switches (seat switch, PTO switch) to determine if the engine needs to be shut down. If a terminal inside the ignition switch or one of the safety switches has vibrated loose, or if dampness/debris has got into the switch housing, it can cause a momentary spike or direct arc to the tractor chassis.

Troubleshooting Strategy for Intermittent Electrical Issues:
Since static resistance checks are passing, try these dynamic tests:

1. The "Wiggle Test": With the tractor key in the ON position (engine off), vigorously wiggle the wiring harness along the engine block, firewall, and dash area while a helper watches the fuse or a multimeter set to continuity.
2. Linkage Inspection: Manually move the stop solenoid plunger by hand. It should stroke completely freely with zero binding. Clean any oil, dust, or grass buildup around the injection pump pivot.
3. Amperage Draw Test (When Hot): After a long mowing session when the machine is thoroughly heat-soaked, clip an inductive amp clamp around the stop solenoid feed wire and cycle the key off to capture the peak rush current. If it spikes excessively high, the solenoid or the linkage is at fault.

 

[North Idaho Wolfman]

There are three fuses that control that system, which fuse are you having to replace?
Each fuse will point to a different issue.
And replacing the fuse with a self resetting circuit breaker will really help you to trouble shoot the circuit.

 

[Hugo Habicht]

Check in the wiring diagram what circuis and switches this fuse supplies. It is very likely hat the short to chassis is caused by wiring or a safety switch.

Replacing the fuse by a 12V bulb with similar current rating will give you an indication when short is present. Easier than replacing fuses or flipping circuit breakers.

Could you post a picture of the relevant schematics here?

A friend of mine had the same problem (different tractor though). I suspected the run solenoid too initially, but it is a two coil design with fairly little holding current, so it does not get very hot. Problem here may be if the pull in coil switch (internal to the coil) is faulty. This current would certainly blow the fuse. You can exclude the coil by unplugging it and use the tractor and see if fault remains.

In my friends case it was a faulty seat safety switch.

 

[BX25D Rookie]

I mowed today at the house. Before I started the BX 2370, I unplugged the engine stop solenoid.
The fuse that has popped twice is in the lower right corner of the fuse box. 10 Amps. Labeled Timer/Relay.
Looking at the second schematic, that 10 Amp fuse doesn't appear to directly power the engine stop solenoid.

Full Schematic:

BX1870, BX2370, BX2670_Tractor Mower loader WSM_a.pdf by cee_Kamp 32ACP, on Flickr

Partial schematic, OPC:

BX1870, BX2370, BX2670_Tractor Mower loader WSM_b.pdf by cee_Kamp 32ACP, on Flickr

It was hot today when mowing, almost 90 Fahrenheit. Two hours for completion, the Kubota didn't miss a beat. With the engine stop solenoid unplugged, turning the key off didn't do anything (as expected) so I opened the hood and pressed the stem on the solenoid and the motor shut down.

I really don't have the time or inclination for fooling with the tractor right now.
With the better half's ALS diagnosis, I don't have any spare time at all, being a full time caregiver.
I think I will buy a box of the 10 AMP fuses and call it good until it's a hard failure, 100 % of the time.
When that 10 AMP Timer/Relay fuse pops, the tractor stalls, immediately re starts when you turn the key, and then you have to manually push the Engine Stop solenoid stem for shutting the motor down.

 

[PaulL]

I'd be inclined to leave the solenoid unplugged, and open the hood and push the solenoid to stop the tractor each day. Advantages:
1. Potentially no need to replace fuses
2. Not that hard
3. If the fuse blows again, it tells you it's not the solenoid (or not only the solenoid). If it doesn't after a reasonable amount of time, it probably tells you it was the solenoid
4. When you do have time, it gives you a fair hint that you need to replace or remediate the solenoid, which isn't that hard a job once you have headspace

 

[stephenrobinson98741]

First, I already have the workshop manual. And the wiring diagrams/schematics.
Second, I have several Fluke digital multimeters. And clip leads along with various jumper wires.
Third, I have 20+ years experience as an ASE Master Certified Auto/Light truck technician.
Doing electrical/fuel injection/computer controls diagnostics & repairs professionally.
Fourth, I do all of my repairs and maintenance for all our vehicles here at home.
Fifth, I still have all of my tools from the car/truck days.

The above being said, I am looking for a helping hand where to look for this highly intermittent fuse blowing.
I mowed 97 hours with this machine last year, the fuse popped once on the last mow of the year in October.
Then you can't turn the machine off with the key and have to depress the engine stop solenoid by hand.
I replaced the fuse and the tractor operated as designed for about ten hours.

Yesterday when mowing at the cabin, the timer/relay fuse popped again.
After about four hours continuous mowing.
Today, I replaced the timer/relay fuse again and drove the machine up/down the driveway for about 10 minutes.
Zero problems, the fuse did not blow and all is good again.

For those of you who might work on Kubota BX machines at the dealership level, do you have any suggestions?
What part(s) have you seen that exhibit this highly intermittent behavior?
If I was to go out and test resistances and voltage/amperage right now, everything would test fine.

Sounds like an intermittent short or something overheating once the machine gets hot. Since the engine won’t shut off after the fuse blows, I’d start with the fuel shutoff solenoid and timer relay. I’ve also seen rubbed wires under the platform or near steering components cause random fuse pops on BX tractors. Hard part is they usually test fine until the problem actually happens.