bitseeker
Silver Member
We have a new Kubota GL5240-3. With purchase, we had the dealer install a 3rd function valve to operate a thumb on the FEL or the elevation deflector on a snowblower. The valve is electrically-actuated by two switches (up & down) on the FEL control stick. The dealer did not have quick disconnect couplers and terminated the outlet tubing on the FEL with caps. I added quick disconnect couplers of the same type at the tractor-to-FEL connection.
I bought and mounted the Green's Thumb after getting the tractor home, and it has not ever worked correctly, and operation just got worse (none!). I'd appreciate suggestions and criticism of the troubleshooting steps and my conclusions so far.
Thumb operation was different at different times. Sometimes the thumb would not open and sometimes it would not grip strongly. After cycling or raising and dumping the bucket, operation would change.
1. I thought I had a bad QD coupler that was blocking flow in one direction, and changed it. Now I am not sure that the coupler was the source of that problem.
2. To eliminate the chance that my hoses or couplings were bad, I made up and attached Male-to-Female coupler loop hose and attached it to the FEL attach couplers in place of the thumb cylinder. The switches made hydraulic fluid flow in both directions with no apparent flow restriction (no engine load), but the hoses did exhibit some pressure.
3. I replaced the Thumb open and close (cylinder extend and retract) hose from FEL to Thumb's cylinder (replaced with test hoses, test coupler-ends and no flow-restrictors at the cylinder).
- Engine RPM = 1,000
- Thumb opens all the way
- Thumb opens slowly (40 seconds).
- Thumb has some open force, but will not quite lift 175 pounds.
- Thumb closes slowly (10 seconds) with no switch actuation. (Will not stay open.)
- When the thumb closes slowly, as above, I cannot restrain slow closing. Hydraulic pressure seems to close it.
The above tests indicate that none of the operational hoses, couplers, or flow restrictors were the cause of the thumb problems, because all of the operational parts have been replaced.
4. Other observations:
- After FEL operation (Lift, Curl), and rapid thumb open/close commands, the Thumb stopped operating completely.
- With 3rd function defeated (switch up, light off), both 3rd function hoses have pressure (expand on engine start, relax on engine stop)
After the operation got worse, I did the following:
5. The Nachi P-SK-GO1-C7Y-GPT-D1-5162H 3rd function valve does not click when pressing either the upper or lower switch. The valve used to click.
6. Checking the 3rd function valve electrics, the switches are sending 12-volt power to the valve.
7. Each of the solenoids has a resistance of approximately 5-ohms, which seems correct.
8. Both output hoses have pressure when the engine is running, even with electric power defeated (light off).
9. With the engine off, I can manually cycle the cylinder full range, forcing oil in either direction through the valve. Looking at the valve specification, I believe that it is spring-centered, with both output ports blocked when centered, and should block flow, stopping cylinder motion in the valve's center position (no voltage to either solenoid).
10. With the engine running, because the extend/clamp-side of the Thumb cylinder has more area, the Thumb is clamped closed. I cannot use the FEL in this condition, and will have to at least remove the thumb.
11. Because of the 3rd function valve, the pressure will be on both the open and close hydraulic lines to the couplers on the FEL at all times the engine is running. This loads the engine, and seems like poor practice. I do not think I should operate the tractor like this. Correct?
12. From the above, I conclude that the valve's internal shuttle is stuck in a partially open position, and that the solenoids cannot move the shuttle.
Please give me any ideas and opinions you have on this problem.
Any ideas on what to do next?
Thanks
I bought and mounted the Green's Thumb after getting the tractor home, and it has not ever worked correctly, and operation just got worse (none!). I'd appreciate suggestions and criticism of the troubleshooting steps and my conclusions so far.
Thumb operation was different at different times. Sometimes the thumb would not open and sometimes it would not grip strongly. After cycling or raising and dumping the bucket, operation would change.
1. I thought I had a bad QD coupler that was blocking flow in one direction, and changed it. Now I am not sure that the coupler was the source of that problem.
2. To eliminate the chance that my hoses or couplings were bad, I made up and attached Male-to-Female coupler loop hose and attached it to the FEL attach couplers in place of the thumb cylinder. The switches made hydraulic fluid flow in both directions with no apparent flow restriction (no engine load), but the hoses did exhibit some pressure.
3. I replaced the Thumb open and close (cylinder extend and retract) hose from FEL to Thumb's cylinder (replaced with test hoses, test coupler-ends and no flow-restrictors at the cylinder).
- Engine RPM = 1,000
- Thumb opens all the way
- Thumb opens slowly (40 seconds).
- Thumb has some open force, but will not quite lift 175 pounds.
- Thumb closes slowly (10 seconds) with no switch actuation. (Will not stay open.)
- When the thumb closes slowly, as above, I cannot restrain slow closing. Hydraulic pressure seems to close it.
The above tests indicate that none of the operational hoses, couplers, or flow restrictors were the cause of the thumb problems, because all of the operational parts have been replaced.
4. Other observations:
- After FEL operation (Lift, Curl), and rapid thumb open/close commands, the Thumb stopped operating completely.
- With 3rd function defeated (switch up, light off), both 3rd function hoses have pressure (expand on engine start, relax on engine stop)
After the operation got worse, I did the following:
5. The Nachi P-SK-GO1-C7Y-GPT-D1-5162H 3rd function valve does not click when pressing either the upper or lower switch. The valve used to click.
6. Checking the 3rd function valve electrics, the switches are sending 12-volt power to the valve.
7. Each of the solenoids has a resistance of approximately 5-ohms, which seems correct.
8. Both output hoses have pressure when the engine is running, even with electric power defeated (light off).
9. With the engine off, I can manually cycle the cylinder full range, forcing oil in either direction through the valve. Looking at the valve specification, I believe that it is spring-centered, with both output ports blocked when centered, and should block flow, stopping cylinder motion in the valve's center position (no voltage to either solenoid).
10. With the engine running, because the extend/clamp-side of the Thumb cylinder has more area, the Thumb is clamped closed. I cannot use the FEL in this condition, and will have to at least remove the thumb.
11. Because of the 3rd function valve, the pressure will be on both the open and close hydraulic lines to the couplers on the FEL at all times the engine is running. This loads the engine, and seems like poor practice. I do not think I should operate the tractor like this. Correct?
12. From the above, I conclude that the valve's internal shuttle is stuck in a partially open position, and that the solenoids cannot move the shuttle.
Please give me any ideas and opinions you have on this problem.
Any ideas on what to do next?
Thanks
