Kubota KX-91 3 SS2 Thumb Issue

[DM1]

Hydraulic thumb stuck in open position.

Problem started with thumb not functioning at startup. Shut down machine and restart would correct issue. Got progressively worse and would fail at random times during operation. Again, shut down, wait 30-60 seconds and restart would correct the problem.

Now, went to total failure. Stays loaded in the open position (whether or not the aux control is activated). Unloads by lifting the lockout arm. Changing the valve to one way releases pressure. Occasionally I can hear the pump load when moving the rocker SW on the joystick but not always. Swapped the connectors at the proportional solenoid valve and the thumb goes to closed (not open).

At this point, it seems that - (1) the rocker SW is bad. (2) the main control valve block is stuck (3) the SW for hammer operation is stuck in the operating mode (4) computer has failed (5) I have a wiring short.

 

[DM1]

Have replaced the Joystick, rules out the rocker sw. No change in the problem. If the main control valve were stuck, it would seem that swapping the wires at the solenoid would NOT cause the problem to reverse. Changing the Joystick also rules out the hammer operation sw being stuck. Guess I am replacing the computer (IC) unit next. $$$$ going up!

 

[North Idaho Wolfman]

Do you have the WSM for the unit?

 

[GreensvilleJay]

really need WSM or at the very least wiring diagram.

hopefully the solenoid coils are field replaceable. if so swap in another, for test purposes. be nice if there was an LED on the coil so you could SEE it was getting power....( <$1 to do that )
hard to troubleshoot over the internet......

 

[DM1]

Do you have the WSM for the unit?

Yes. have followed as I can with no sucess resolving the issue.

 

[DM1]

really need WSM or at the very least wiring diagram.

hopefully the solenoid coils are field replaceable. if so swap in another, for test purposes. be nice if there was an LED on the coil so you could SEE it was getting power....( <$1 to do that )
hard to troubleshoot over the internet......

Have swapped feed wires to the solenoid coils and reversed the issue. Coils seem to be working as well as the hydralic flows they control.

 

[North Idaho Wolfman]

So your issue is in the electrical control portion.
I don't have the WSM for that model, I'll see if i can get it.

Can you control the thumb at all?
In other words is it getting power to the thumb valve all the time or is it only when you move the switch?

If it's only getting power to move it in one direction when you use the switch, and nothing in the other direction, then I would think there might be a relay that is not working properly to allow it to flip the signal to the solenoid, or it could be in the programing portion, thinking it's a no reversible motor circuit.

Tell me more about what your seeing on the control wires and when.

 

[DM1]

So your issue is in the electrical control portion.
I don't have the WSM for that model, I'll see if i can get it.

Can you control the thumb at all?
In other words is it getting power to the thumb valve all the time or is it only when you move the switch?

If it's only getting power to move it in one direction when you use the switch, and nothing in the other direction, then I would think there might be a relay that is not working properly to allow it to flip the signal to the solenoid, or it could be in the programing portion, thinking it's a no reversible motor circuit.

Tell me more about what your seeing on the control wires and when.

I have both the WSM and the supplemental minor change update. I think it was getting 5v to the sw. Power on at all times to the open position, no change going to the close position. Reversing connections at the pilot solenoids causes the issue to reverse (thumb goes to full close not open). Replaced the Joystick with a new one. Just sent the IC box off for rebuild.

 

[North Idaho Wolfman]

I have both the WSM and the supplemental minor change update. I think it was getting 5v to the sw. Power on at all times to the open position, no change going to the close position. Reversing connections at the pilot solenoids causes the issue to reverse (thumb goes to full close not open). Replaced the Joystick with a new one. Just sent the IC box off for rebuild.

Let us know if that fixes it.