Just as the subject states, I have a hydraulic cylinder that only moves in one direction. I forget if it moves in or out but its on the offset boom on my komatsu pc128, any ideas what to look for before I have someone else try and fix it.
is the controls valve a foot pedal on th floor? I'd be checking there's no dirt jammed in around the valve jamming it up or seizing the valve could be a valving issue or a broken piston in the ram, bet way to isolate the problem is swap the hoses on the ram (if you can) and is the fault swaps to the other direction you know its a valve issue, if it won't move in the same direction theres a problem in the cylinder (broken piston and/or internal seals)
If the offset boom won't swing back toward cab, will only swing right, could also be a problem with the boom position sensor system. I haven't worked on a PC128, so not certain, but Komatsu offset boom machines that I've worked on has sensors to monitor position of boom to prevent operator crashing bucket into cab.
I found a way to bypass those position sensors years ago when they started acting up and prevented the boom from moving by flipping a hidden switch under the seat. I checked the the foot pedal and cleaned it without any luck but switching the hoses sounds like a good idea. I will try and do that the next chance I get and see what happens. Thanks so much for the help with this.
Ok I finally got a chance to swap the hoses on the cylinder and this does in fact allow the piston to move in the other direction so Im assuming its a valve issue like stated below. I took apart the foot pedal and did not find anything wrong there. How do I go about checking the valves? And what are all those soleniods with the two wires connected to the top of them and how do I trouble shoot those and what is their purpose. They seem to be on every hydraulic valve on the machine.
Imagine my surprise when I got on a fairly new and large (think CAT 966) Volvo loader in 2003 and discovered down pressure could not be applied to the bucket, the damned thing was gravity operated. The rest of the machine was equally half-a$$ed. A POS if there ever was one.
You can verify if it is the FOUR (sic) system in protection mode by holding the rubber covered override toggle UP, which is located in a recessed box under your right kneecap, when seated in the machine. By holding the switch up (which will be accompanied by a buzzer), you can defeat the FOUR system, but, use care to not ram the bucket into the cab. If that allows control of the offset both ways, we can get into details of how to diagnose and repair it.
Is your pattern change valve half cocked?
I actually have that toggle switch locked in the up position because I just never felt like dealing with all of the pitfalls of the system. Never rammed the bucket into the cab yet, nock on wood. What and where is the pattern change valve. thanks
Pattern change valves switches from cat to John deere controls. It is usually in one of the rear compartments. Sent from my DROID RAZR using Tapatalk 2
Still trying to solve this problem to no avail.
Pattern changer (if it has one) has no affect on offset boom control as it's not on the joysticks, controlled by a foot pedal instead. Gunite, I'm confident the sensor system is what's preventing you're boom operating in one direction, you're either going to have to find the problem and fix it, or locate the solenoid that dumps pilot pressure oil for offset control and bypass it or disable it. I have no clue where these solenoids would be on a PC128 as I've never worked on one. But if you open up your floor plate, locate the hoses connected to the foot pedal valve for offset boom, see if you can follow one of those hoses to a solenoid valve, that would likely be the valve that's locking out your boom offset in one direction. But before you bypass or disable the solenoid, at least give a look to your boom components. The sensor potentiometer that monitors boom offset will be located at the pivot point of offset boom. It's a round object with two wires going to it, typically has an arm on a shaft and linkage connecting that arm to the offset boom. Check those components to make sure they are intact and not damaged, also inspect the wiring harness coming from potentiometer and running down boom to machine.
A few years back I had a problem with the sensor potentiometers acting up so i called komatsu and they sent someone to the job site to fix the problem because I couldnt move the boom at all. It completely locked up everything. He flipped a toggle switch under the seat to disable the entire system and charged me $750. So with that said do you still think i should try and locate the solenoid valve.
That sucks that dealer couldn't do better than that. However, it's hard for me to say for absolute certainty what you should look for or repair. I'm only saying, it does sound like the sensor system is what is keeping you from operating the offset cylinder in one direction, that's what it does. And there's only two ways I know to remedy the problem, either fix the system to work proper, or find the solenoid that controls the function that is awry and bypass or disable it. The problem with remedy #2 is this increases the risk of operator sticking bucket into the cab, as that's what the system is designed to prevent. When you disable that system, operator must keep his wits about him.
ok, all this info is going to help me solve this problem at some point im sure. Even if i bring it some where I can at least give them a better Idea about what I checked and found so far. Ill keep you updated, thanks for all your help.