Chugach-Ven
New Member
Situation: Hey, I have a Hitachi ZX40U-3 excavator. I am adding aux hydraulics to use a thumb. The way I have set it up, I have a solenoid activated directional control valve (sharing image below) installed into the pilot hydraulic system. T'd into pressure and tank lines. A & B lines going to the main control valve where there is an existing but unused auxiliary valve. I have all the manuals so I have confirmed it is aux valve (also sharing image from manual). Plumbed hydraulic lines from aux valve in main control valve to the end of stick and into thumb cylinder. The pilot control valve is controlled via buttons (not rocker) on new joystick.
Problem: Each time I press the button on joystick to move the thumb in a direction and let go, the hydraulic flow appears to continue as the thumb will keep moving in that direction until a) it hits bucket or is fully retracted or b) I hit the other button in which case the thumb will change directions but again continue to move even if the button is released.
What I thought it could be:
Residual voltage keeping pilot valve open: I have tested the voltage coming from buttons to solenoid and it drops appropriately from 12v to 0 after button is released. I have installed a thumb on another machine and I had an issue with voltage spikes ruining the button switch so I have installed rectifer diodes in parallel to dissipate on these solenoids as well. No change after.
Faulty pilot DCV that isn't returning to center: the pilot directional control valve has manual push to return to center. I can't exactly move fast enough between pushing the joystick button and pushing the manual pin to see the thumb stop in mid stroke, however when I push the manual return on the DVC it doesn't stop the thumb from pushing against the bucket or the arm. So not ruling this out but it doesn't appear to be this.
Needs an overload relief valve installed on main control valve: There are two ports (currently plugged) for overload relief valves on the aux part of MCV. I thought these being missing may be part of the reason its not working properly. I then switched the bucket relief valves and installed on aux valve of MCV and no difference.
The only way I can get the thumb to stop moving once it has been activated is to turn the machine off. The interesting thing is, once I turn the machine back on, the thumb is still, it won't move in one direction or the other unless activated again.
Any help would be greatly appreciated.
Eric
Problem: Each time I press the button on joystick to move the thumb in a direction and let go, the hydraulic flow appears to continue as the thumb will keep moving in that direction until a) it hits bucket or is fully retracted or b) I hit the other button in which case the thumb will change directions but again continue to move even if the button is released.
What I thought it could be:
Residual voltage keeping pilot valve open: I have tested the voltage coming from buttons to solenoid and it drops appropriately from 12v to 0 after button is released. I have installed a thumb on another machine and I had an issue with voltage spikes ruining the button switch so I have installed rectifer diodes in parallel to dissipate on these solenoids as well. No change after.
Faulty pilot DCV that isn't returning to center: the pilot directional control valve has manual push to return to center. I can't exactly move fast enough between pushing the joystick button and pushing the manual pin to see the thumb stop in mid stroke, however when I push the manual return on the DVC it doesn't stop the thumb from pushing against the bucket or the arm. So not ruling this out but it doesn't appear to be this.
Needs an overload relief valve installed on main control valve: There are two ports (currently plugged) for overload relief valves on the aux part of MCV. I thought these being missing may be part of the reason its not working properly. I then switched the bucket relief valves and installed on aux valve of MCV and no difference.
The only way I can get the thumb to stop moving once it has been activated is to turn the machine off. The interesting thing is, once I turn the machine back on, the thumb is still, it won't move in one direction or the other unless activated again.
Any help would be greatly appreciated.
Eric
