Hitachi PVC question

[Syleng1]

Quick question:
Hitachi EX120-2
My hydraulics are getting slow after warm up - previously I asked questions about swing only but now tracks are slowing and eventually the arm and boom movements are getting choppy after run time.
0-20mins all is well
20-30 mins of time loose swing speed
30-35mins tracks start slowing down
35-50mins the bucket functions start to slow and get choppy. Kinda like very jerky and not smooth. I’m working with pressure gauges per manual and find my pilot pump is working at 1000psi always.
the fluid is getting hot like it’s going around the relief valve kinda like the warm up circuit is not shutting off.
I trace all the electrical connectors from the valve bank back to the PVC. All ohm and voltage check okay. If I connect all the solenoids I loose hydraulics. If I disconnect the solenoid (in manual page w02-11-02a) called the solenoid for parking brake- the hydraulic all function properly. Connect it and the solenoid stays on the “electrically on” position which is hydraulically “off.”

so my long question is- if I can trace my harness from this solenoid electrically back to the harness pvc connector and it is not open or shorted to ground (circuit# 112(-) and circuit#110(+) to fuse #9) does this mean I have a bad PVC keeping the brake for the swing “on” and this is not allowing the computer control the pressure electrically?
I recently ordered the DREX on line and waiting for that to arrive. I see where there is a pilot relief valve and a pressure reducing valve and how to adjust. I’m just worried if the machine is bypassing the valves Due to lack of electrical control the fluid is getting too hot and Causing my issues. Any thoughts?

 

[mg2361]

Connect it and the solenoid stays on the “electrically on” position which is hydraulically “off.

Does it go electrically off when a dig function is activated? If it does then it is working correctly.

Need to establish a baseline. Pilot pressure is 1000 psi, a little high but we will deal with that later. What is the reduced pilot pressure? What is the system relief pressure setting when it is working and when it is not working correctly?

We also need to establish if there are codes. May have to wait until you get your tool. There is a procedure to get blink codes.

With the tool then we can determine if all the pressure sensors are doing what they are supposed to. A false reading from one or more sensors can play he@* with the system.

Maybe with luck Lachau will chime in on this machine with some words of wisdom.

 

[Syleng1]

Sorry- please expand your post to see my answers. I’m not the best with this type of message mg2361

Does it go electrically off when a dig function is activated? If it does then it is working correctly.

The solenoid in question stays electrically “on” which keeps the hydraulics off. I have units called “noid lights” that plug into the harness. The bulb is on always but goes off with the key. So if I plug it in the solenoid works properly and shuts off the hydraulics to all functions. After reading the section in the FSM about operation. The pvc is supposed to “pulse” the ground wire circuit 112 to control hydraulic pressure. I have constant ground and 24vdc at that plug. It was disconnected when I bought the machine. Not to repeat but I did ohm both wires to the source power and ground, looking for short to ground, open and draw test. From end to end it is a solid path. The PVC is commanding the wire grounded due to 1 of the following issues as I see it.
A) pvc is bad.
B) something else is not working properly giving the pvc bad info telling the pvc to command solid “on”
C) mechanically the pressure is high due to another making adjustments mechanically and the pvc is out of sync with the new corrections.

my Dr-Ex is due In next week. So manually adjusting pressures with shims is not a good idea. I changed the hydraulic filters - all clean and no metal after 40hrs of use. Oil temp is hitting 125 degrees f. And holding. I pulled out the relief and pressure regulators and checked for metal, movement and broken springs... all good.

Need to establish a baseline. Pilot pressure is 1000 psi, a little high but we will deal with that later. What is the reduced pilot pressure?
750psi

What is the system relief pressure setting when it is working and when it is not working correctly?

correctly 4500psi
Poorly under 2500psi
“If” I am answering your question correctly.

We also need to establish if there are codes. May have to wait until you get your tool. There is a procedure to get blink codes.

understood.

With the tool then we can determine if all the pressure sensors are doing what they are supposed to. A false reading from one or more sensors can play he@* with the system.

Maybe with luck Lachau will chime in on this machine with some words of wisdom.

 

[Syleng1]

Just an update for the future needs of the masses.
So I purchased the software and cable for inside the brain info. Nothing.
I decided to change out the pilot filter and top off the hydraulic oil from leaking cylinder. So far the machine (knock on wood) has worked properly and no more over heating of the oil, the cylinders stopped leaking and the machine is operating properly. All from a simple filter.
I am very fortunate as I’ve read a lot of horror stories about this same issue.