I have a 75XT that I’m running out of options on. The boom will lift seemingly normal, maybe a little jumpy, slower, and when you try to lift something heavy it will bypass out and won’t lift. Can handle a bucket, but not much more.. when the boom is all the way up, it will labor hard hard to lower and takes probably 20-30 seconds to get boom all the way down. It acts as the aux is stuck on. When that happens you can’t do two things at one. Aux is NOT stuck on though, but when you raise boom, and try to curl at same time, you cannot. Can only do one or the other. Tilt works fine, no laboring. You can put in float and it will settle down with no laboring- Now for what I’ve tried- - I have no self leveling valve from what I can tell, lines come out of control valve and t off and go straight to each boom. I looked up what the valve looks like and cannot find it anywhere. 95% sure I don’t have one. -boom does not settle when off and left up overnight. -hydraulic Power quick tach and park selenoids work as should it seems - all safety switches are working or bypassed (seat, lap bar, door, and cab lock. - spool valve selenoid on back of control valve towards motor is magnetizing as it should, however, the odd thing with this is… whether it’s magnetized or not; the lift and lower acts and does the same thing. I pulled the spool out though, set it on bench, put power to selenoid, and internally it retracted as should, about a quarter inch, then popped back out when shut off… so this seems to be working. But not sure why it doesn’t change the operation… - pulled top relief valve; all o-rings and seals are good, oil clean, no blockage. -pulled both spool lock valves for tilt and lift, they’re working as should because I’m able to move handles side to side; then they lock when machine is shut off. -started pulling some of those hex nut reliefs? They look clean, just a little metal plunger and spring inside. -locked boom up; and tied each cylinder together so they take lift cylinders out of equation. Top to bottom; top to bottom, on each side. The motor labored down and up this time; which I thought was odd? But never done this before so not sure how it’s supposed to sound- I thought with no resistance it would just barely labor if any. - questioned about pulling lift spool out, but it goes in and out smoothly, and I would think it something was off inside, the boom would settle or drift down if not centered? Didn’t check into this though. It doesn’t have abnormal settle I’m about out of options… I would think it has to by cylinder or control valve related? Because it drives perfect with no laboring at all… purrs like a kitten, and tilt appears to work just fine; but the no lift power hardly, and hard labor on lowering the boom, is boggling me.. if you made it this far, thanks in advance. Any help is appreciated. Thank you!
Is there a counterbalance valve(s) on boom cylinders? I’m sure whoever does have access to the info about innards of this machine ( I don’t ) will tell you whither there’s pilot operated check valves in the control valve section. What you described is sounds like counterbalance or PO check valve malfunctioning, or someone messed the hoses up. Could be restriction somewhere, “flapper” in the hose. One thing you need to remember, when you retract cylinder, you push a lot more oil out of blind end of the cylinder, than you pushing in to rod end.
I’m unsure about counterbalance, but don’t believe so- I’ve considered looping a 1 foot hose out of control valve and right back in, to take entire hose sections and cylinders out of play. This is a picture of control valve, I’m unsure what aluminum block on end closest to motor is..
Both counterbalance and PO check valve work in such a way, that they will not let the oil out, until the pressure on the other side will build to certain level. Counterbalance also controls the flow and it’s adjustable. Do you happen to have hydraulic diagram for this thing? Or should we wait for someone who does?
Aluminium block, most likely is spool shift switch housing, which doesn’t come standard with the control valve. So they machined it to be switch and centering spring housing at the same time.
Pulled up the parts book, aluminum block is detent housing, for your float position. No idea what that sensor or switch is - it’s not in that diagram.
There is a counterbalance valve. It’s on the opposite side from that aluminum detent housing, next to spool lock solenoid
Item #13. See if any O-rings on it is bad or very flat. Moisture/corrosion issues
So that part is what they call “cavity plug”. That’s to populate the space where counterbalance valve is supposed to be. Your machine might have the valve itself in it, instead of that plug. Or that plug have bad O-rings on it and leaking pressure to the blind side. And looks like it’s Sun Hydraulics product also.
There’s two types of the control valves on those machines. Yours looks like might be Parker VDP family. The problem that CNH pretty much expapropriated the whole VDP line up long time ago. So nothing on Parker general information is available. It is highly proprietary to CNH now.
I greatly appreciate your knowledge and research spent on this issue I’m having. I took your advice and did find a counter balance valve. You were right! I removed it and the end was cracked off. I went fishing with a magnet and found some (I hope all..) the pieces. - why would this happen? This must be allowing fluid to get where it shouldn’t I appears? - I went to a case diagram and the only visual they show with a counter balance valve, they don’t give it a part number… I’m unsure why.. they do give a part number for the plug though? - assuming I can find a counter balance valve, maybe there’s a greater issue though? The entire control valve is pricey… Thank you so much! Visually seeing an issue is a relief. But now comes the “how to solve it” part.. haha
Is your oil have water In it? Maybe something got frozen. That usually happens on what’s called “pressure intensification”, works on effective are differential of the cylinder. Basically 100 psi if pressure on the blind end, will build 300 psi of pressure on the rod end, if the rod end outlet is blocked somehow. And 3000 psi on the blind end - can induce 9000 psi on the rod end.
Is there any markings in the hex head? If you can’t get the valve itself, you might try to get that cavity plug, it should in theory restore the functionality, but without locking security of the counterbalance valve. That’s if your spool is not “motor” centre. Usually with counterbalance and PO checks they use “motor spool” and without “cylinder spool”. Looks like you will have to contact CNH dealer with your serial number.
Unfortunately I’m naive in this category of mechanics.. I’m not sure if my oil has water in it, but doesn’t appear to? I guess I’d have to drain it all out from bottom if I can find a drain to tell for sure.. a possibility I suppose. -no part numbers marked on the valve unfortunately… - I’m not sure what you you mean but so much pressure being built and blind and and why. - also what is the purpose of the counter balance valve , and what do you mean by replacing it may still work, but without being able to “lock”? - also unsure what a PO valve is… This is a category I lack knowledge… but trying to learn! Thank you!
That’s what I dig up so far. Looks like it’s not serviceable part.
You will need to find out what is your control valve part number. Because there’s three different part numbers for the control valves, and three different part numbers of the counterbalance valves for them.
Maybe this will help with part numbers, listed in the later series machines. As to why it has exploded like that I can't really say - but all pressures should be checked before any work is done with the machine, if the new part can be bought & fitted (Used) - they are listed as no longer available.....Ebay currently shows a 446619A1 counter balance valve edit - after looking at pics again, I think you have a broken flow control valve - 397967A2 - CARTRIDGE
Cylinder had blind end or piston end, that’s the side without rod. So the area of the circle that occupied by rod substruct from the effective area of the circle of the piston. The force acting on the piston is total affective are of the piston times pressure. And because the blind side doesn’t have the rod reducing the effective area - force will be higher. When piston moves, it pushes on oil, if oil have no way to escape, it will be building up pressure, and because of the difference of the effective areas of the opposite sides of the cylinder is different - pressure build up will be different. I’ve actually had one of the counterbalance valves stripping the thread out, and flying away 25 feet, almost hitting me, because the hoses to the cylinder was installed wrong. It was little bit more complicated than that - but that’s just for example. Important thing is - it created pressure intensification, that blew the valve out of the block. So most likely some passage got blocked ( maybe even with ice, frozen water in oil) or someone installed hoses to the cylinder wrong ( not sure if someone worked on hoses). Counterbalance is holding the pressure ( not letting oil through) until that pressure will be higher than set spring force, or the pressure from the other side of the cylinder will open it up. In other words, the normal load of the material in the bucket, will not open the valve, until you will introduce pressure from the rod end of the cylinder. Without counterbalance, that function is fine by control valve spool, but spools are not “leak free”, like counterbalance valves, they leak slowly, so the bucket will be creeping down slowly.
Nice.
That actually looks more like the valve you have. Because it shows that switch in the detent box. And that valve being a flow control makes better sense, because it is in the inlet section. And items 17 and 19 are more looks like counterbalance valves. So you need to check whether those valves are in your control valve also. There’s superseding pert numbers, but they are very proud of those. Looks like Sun Hydraulics valves, but I’m sure they will not have Suns numbers on them. That’s how CNH makes money on parts.
And all of that comes up as self leveling machine. I think you might be mistaken that your machine is not.
I appreciate your thought our response explaining how this all works! I understood the great majority of that. Is this the same bypass as when you run your aux hydraulics without anything hooked up? Or continue to raise book even though it’s all the way up? You hear it bypass? I assume not. That must be another passage… It’s possible someone hooked it up wrong at one time. We purchased the machine this way.. although, I have purposely hooked up hoses backwards on tilt cylinders (different machine), so to bend back a quicktach plate. Is that a bad idea for future reference? The cartridge AlRman posted does appear to be the same part. Mine is chewed up at the end as shown in pics I posted earlier, the internals are what broke though.. sounds like I mainly need what’s inside of that cartridge.
That cartridge is the flow control valve. Not sure it’s functionality, but you might have auxiliary control valve separate from lift/tilt, and that’s what it is for. If you replace both hoses on both cylinders, without crossing them - it’ll be ok. But if you cross them over, as one hose will go to blind end, and one to the rod end, and they came from the same port on the control valve - that will do it.
The bypass hissing you hear when dead heading cylinder or using auxiliary without anything connected to it - is port relief and/or main relief valve. Conterbalance are of “load holding” or “position holding” sort, not circuit pressure protection.
On the past machine I’m referring to (not this one). I did cross them . So that one tilt cylinder was pushing out, one was pulling in, to bend back a quicktach plate. Luckily it survived when I did it. But now I know maybe that’s not so good of an idea. I was thinking it wouldn’t hurt anything. It’s possibly it’s a self leveling unit, but the valve pictured below appears to be no where on my machine… I’m told the lift lines would come out of control valve and go to this self leveling valve, then to lift cylinders. Mine just t off and do not go through a valve. Also, I do have a separate aux valve indeed.
It’s just pictures with parts that match yours referred as self leveling machine.
I did see a control valve on eBay, that matched mine. And seller referred to it as a self leveling version. I assume that may be what you’re referring to. Maybe it’s internally leveled and the separate valve isn’t needed on my machine.. unsure..
Also I didn’t even go to self leveling sections in parts system, and that’s why pictures I’ve posted does not really match what you posted.
You should check whether you have items 17 and 19 on your control valve. Those are conterbalance valves. You might still have problems with them.
Still don’t know what that flow control is about. If the machine had steering and brakes - it would be steering priority flow control. Maybe it is for auxiliary
Have you just bought this machine? Or you use it a good while, and everything was fine?
We purchased the machine the way it is now a year ago. Have not been able to use it as intended. And finally got around to getting it into shop. Regarding item 17 and 19, what diagram are you referring to? The ones I see on case diagrams represent an o ring and selenoid.
I think I’ve found control valve like yours on eBay. It’s $1500. Two counterbalance valves. In in the bulge in between spools, another on the “back wall”, down and left from “out” port. I need to see hydraulic diagram of this thing. Composition of it is goofy. Looks like one too many port relief, one to many load check. I see two spool lock solenoids, but there’s another solenoid, don’t know what that is, “return to dig” electric detent?! Does have flow control for something, but then again has PB ( power beyond) port. It means there should be two more remote circuits that powers up through this control valve. One is flow controlled ( not sure whether priority or not) another simple downstream feed.
I think maybe previous owner eliminated self leveling valve, didn’t know how to connect hoses correctly without it. Couldn’t figure it out - and sold it to you.
Circled yellow - item number 19. It’s on the back, down and left from the “out” port in the middle of the “back wall” Circled red is item 17, it’s in the bulge in between spools, on top plane, where rest of the hoses connects to. Both counterbalance valves I think they are the same, just with different factory preset pressure setting
Circled green is item 19 Circled red is item 17
It’s possible that previous owners eliminated self leveling, but it looks like factory hose routing to me. All metal lines in the tub, and plumbed clean. I believe my control valve has both circled items. I didn’t realize they were #17 and #19 the way the second digit is cut off. Thanks for the clarification. Regarding you mentioning that two more circuits could/should go through the control valve; could it be the power (hydraulic) quicktach, and the park brake? Power quicktach having small cylinders may be flow controlled? There are two smaller golden valves with selenoids on them located inside the tub and mounted up. I figured one may be for power QT and other possibly park brake. I will remove those two counter balance valves tomorrow morning. At some point I may just have to pull the entire control valve, just nice to be able to replace parts and retry its operation with the control valve still being mounted in place. As always- appreciate you!
Quick tach should be controlled through this system. Is your machine hydraulic joystick controlled, or linkage/cable? Parking brake usually gets powered up from drive system charge circuits, unless your pumps linkage/trunion controlled. Do you have high flow? It seems high flow machines have Parker V20 with external pilot solenoid spool positioner(s), that pilot circuit should come from somewhere, could be drive system charge system, could be sequence Valve “pilot generating” block. I’m not familiar with these machines, I can’t find hydraulic diagram for free, and I’m not about to buy manual for the machine I’m not working on.
Looks like your drive pumps are Danfoss. M46. Those do have pilot servo control circuits, although it is manual displacement control. So all the pilot controls, plus parking brake and two speed - gets feed from there.
for not knowing the machine, you sure understand it’s operation impressively well! Obviously have an immense understanding of hydraulic systems and their operation. You’ve been a great help. My controls are hand controls with hydraulic linkage directly to the pump. One of the small golden valves I was referring to has a line that runs to drive motor, so I assume that is the park brake valve. My machine does not have high flow. I will search into getting a service manual. Maybe the dealer will allow me to snap a pic (doubtful..).
I am hydraulics specialist. Both mobile and industrial. I’m independent, so I don’t know particular brands. When it comes to excavator and skid steer control valves - they are highly proprietary. Even one manufacturer ( let’s say KYB) will make those valves differently only to particular customers specs ( let’s say TCM/Mitsubishi/CAT) So it is hard to know all the intricacies of particular machine, without extensive knowledge of the machine, or having proper specialized literature
I’m not sure, but it looks like A1 port is plugged, and looks like the hose that should connect to A1 port connects to port more closer to that flow control. If that hose goes to lift rod end of the cylinder - that explains it. They are trying to limit flow to the rod end, because when rod end is pushing, there’s many times more flow gets pushed out from the blind end ( different volume between rod and blind ends), and can overwhelm the flow capacity of the control valve. But that’s all just guessing.
See that internal hex plug, if you look very hard there’s A1 casted right nest to it, the thing that looks like bolt head in between B1 and A1 is load check, that thing is always between opposite ports of the same spool. Now next to the yellow plastic cap with word IN casted next - there’s another plastic plug, and that’s where you hose goes to.
I’m talking about this hose
The next to it is IN hose, coming from the gear pump, underneath of its bend, to the right is B1 hose, which should go to the opposite side of the lift cylinders, from where hose I circled goes to.
Seems like that what that flow control is regulating
Here’s a picture of the same control valve that doesn’t have flow control, and it has plastic plug in the A1, plastic ( not steel ) plug means that hole is ready to receive hose adapter
I can certainly tell on your hydraulic abilities that you must be a specialist. Im appreciative of your help more than you know! Regarding the circled hose, you are correct- that goes down next to motor via metal lines, T’s off, and goes to each of the rod ends of lift cylinders (top ends closest to removable cap). Are we thinking counter balance valves could still be an issue? I will remove tomorrow and inspect regardless. I just would like to know what causes the flow control to break to begin with.. I understand ice could be a possible culprit.
Look at the oil whether it’s milky. If it’s milky - it got water in it. Only after you start the engine. If it’s sits overnight - oil and water starts separating, and can look like it is not milky. To other questions - I don’t know at this point
While late to the party, I have been lurking. The seat on that valve, looks hammered to death. Whether it did that after that port cap broke off, I wouldn’t know. Would almost believe someone ran the bucket cylinders into something unmovable and the valve broke, before the pressure relief could dissipate the pressure. Depending on which particular valve that is, auxiliary hydraulics could have been left on and dead headed. Hopefully, you got all the pieces or I would be taking that particular valve block completely out and cleaning.
Welcome to the party! And thanks for your input- I called dealer today and the parts rep was unable to locate the internal spring loaded component that broke (that’s inside float control valve). Although that valve is available to purchase, without the internals it does me no good. I agree, my cartridge is beat up though regardless. Nothing I’ve seen come out has been milky and I’ve been losing a lot of fluid with this test procedure. I even pulled plug on bottom of hydraulic reservoir and it was clean as can be. I would think the bottom there is where water would gather. So should be safe to rule water out. I pulled one counter balance valve, the one between the two spool locks, it looks good, other than me rolling over the seal trying to get it out without removing another component.. my mistake.. i assume the seal damage is clearly from me though. I’ll attach picture. The other one was a little tricky to get at and It appears I may be having to pull the entire control valve anyway.. I’m starting to realize I may just have to buy a complete valve, and try to sell the good components of mine off to make up for the cost… I just don’t want this to happen again if something further down the system caused it, like a plugged line or blocked up cylinder or something from a ripped seal. Would be nice to know the cause…
Meh - don’t feel bad. Those get cut on the tread and rolled all the time. It’s just nature of the beast. Surprise to see all black O-rings and backup rings though. Did it look like it was out before? I’d there any markings on the hex?
I think only for one cartridge CNH wants like $1200. The whole control valve on eBay is $1500. Although you never know the condition of that eBay item.
In that groove, between very top O-ring and middle one - there should be a tiny hole, you want to make sure it is not plugged. It is so tiny, that just about only steel wire brush bristle will go through there. I usually use steel bristle and then try to squirt brake clean with straw through it.
I actually know the owner of Hett enterprises and he’s very honest and Great to work with. I’ve purchased from him privately- So I trust anything that comes from him. The counter balance valves themselves are 1450 and 1650 from case. What the heck! Maybe I can sell mine off for half that since they appear good, and pay for a whole control valve. There is a control valve from a 40xt that appears the same for $1000 plus shipping, I may consider that one also if the seller will work with me on price. Otherwise I’ll be better off purchasing from Hett (someone who does this for a living and I know). I don’t believe the counter balance valve has been out before, but it is entirely possible. The hex looked clean and not marked up from what I remember, probably should have paid attention to that first.
No, that’s a price CNH wants for them. Looks like temper resistant CB series from Sun Hydraulics. But that thing is deeply “proprietary” that’s why they charge for it so much.
I'll throw another thought in here. My guess is that the new 397967A2 cartridge will contain the inner parts that you are concerned about. If it didn't have the internals, it would be described as a sleeve. For the amount of money they are asking for it - my guess is that it is a complete working flow control valve. Edit - I would be shy about fitting a valve from a 40XT - they have multiple valve part numbers & none are the same as the 75XT numbers - the 40XT flow control cartridges also have different numbers than the 75XT.
The counterbalance valves have snap rings in their faces, you can take them apart, inspect for damages and clean them. If no serious damages - you don’t need new ones. The biggest problem is flow control.
Any luck getting hydraulic diagram?
I was thinking: if that flow control feeds auxiliary function - it might have gotten killed by using hammer attachment. Just me pondering.
I checked the little port on counter balance valve I removed, and it appeared clear. In response to Alrman, now that you say that I think you may be right. This is gonna get lengthy, but I hope this all makes sense—- The flow control valve cartridge came out with that inner piece broken and resting inside it. There was also a retainer ring (I believe) that came out with it. See pic I attach. I’m wondering if that retainer ring was supposed to hold the inner components in and it broke. However, the inner component is so thin and the one pictured on cnh website has a thicker internal component. Maybe something is broke off in the control valve? I tried to pull anything else I could put with magnet though and nothing else would come out. I’ll attach some pics of what I’m referring to. I have been unable to locate a service manual. I can possibly buy one on eBay for $50 for a digital copy it appears. Regarding your jackhammer idea, I suppose that could be it too. I’ve never used one of those but they can’t be healthy for the aux system.
I’ve located this valve on eBay, seller said he would accept $750 shipped. I’m considering going that route. It is listed as for a 40xt (may fit others), but it appears the exact same as mine from what I can tell. Seller removed flow control valve and sent me pics. I will need to reseal that it appears. Looks the same as mine. Then maybe I can sell off parts of mine to recoupe cost.. thoughts on this? The one I would receive is the one in the wooden box. The other pics are the new valve he replaced his with. He said the piston nut backed off inside his cylinder and that was the issue and it wasn’t a valve issue.
Pics of flow control inside valve I’m considering purchasing (seller was nice enough to remove and send pics) took same size wrench to remove as mine and appears the same
What is that circled in green, old paper towel residue? Looks the same as yours most likely looked like before it detonated. If you just swap that valve, take everything you can off that block, looks like a Sun Hydraulics block, and it would be prudent to look for leftover pieces inside and possible cracks between passages. I have had a few of those Sun blocks go bad inside with cracks, most likely from the pressure relief valve hammering away and cracking inside. Good luck. In certain applications, we changed out the aluminum blocks for steel depending on what their purpose was. Edit to add, that is not a Sun block, the aluminum one on the side may be though.
The seller thought the green circle was the sealer oring coming apart. Update that’s confusing me.. the valve I’m considering purchasing does indeed look the same in everywhere that I can tell.. however it’s part number is 87431789 and mine is 87431792… I might be best off buying it anyway to use the flow control valve off of? And sell the rest off? I’m not convinced a new flow control valve will solve the issue of mine. I can get just that cartridge for $500. But I’m unsure what happened to the end of mine, I think there’s still a piece missing because the new ones have a capped like end. And mine is just a thin broken end… a whole new/used valve that matches my part number is $2200….
When it comes to those valves and blocks, every different number generally means a different part. When you buy a valve block, they may have some of the same valves, as in the same pressure relief or same function valve but different block numbers mean they are set up a different way. Thats a lot of coin, for a part that you may not even need. I would buy the separate cartridge but definitely clean out block as best you can and verify that where that seat was hammering away, did not damage that block internally.
thank you for your advice, I am going to pull the control valve tomorrow, strip it down and inspect. Im still wondering where the end piece of the flow control valve went…. Will keep you all posted tomorrow evening, thank you thus far!
Reviving this thread as I’ve since worked on this machine again. It has been in the corner of shop… anyway, I did purchase a new flow control valve. I’m not sure why the old one broke… that bothers me. The end broke out for those that remember. I found the end lodged in a pathway ahead of it. With a screwdriver it was fairly simple to knock free and pull out. I had the entire control valve on the bench, pulled each and every component to inspect. Reliefs too. All looked good. Put back together with a new flow control valve. I was certain I solved the issue. The blocked pathway would cause the machine to labor when lowering the boom, right? Only makes sense. However, put together again and same exact symptom… no improvement. I lift, and it lifts better I think? Seems smoother, it was jumpy before, but when lowering, it labors. The laboring sound is the same as dead heading the aux hydraulics with no attachment hooked up (tried it to compare, same laboring). This machine does not have a self leveling valve. I would have thought it was that, but I’m told the lines come from control valve into self leveling valve, then to lift cylinders. However, mine come from control valve and go straight into lift cylinders.. I had beforehand taken each lift cylinder out of play, by just crossing the two lines at each cylinder together, one at a time. Same symptom. So it’s not with the lift cylinders. I suppose my control valve could be damaged, but I’m not sure how.. everything looked fine. I hate the idea of pulling again to further inspect, but maybe that’s all it can be.. Any ideas? Thanks
Somehow I managed to overlook the lower counter balance valve being damaged. A piece of the damaged flow control snap ring had been lodged in the seals. I’m going to a hydraulics shop tomorrow to have it resealed. I’m hoping with the damage being below the sealing surface, it will be okay. I attached two pics My question is. It almost looks like it would have been sealed even with this metal lodged in the seals. Likely not, but let’s just say a little bit of fluid sneaks by that seal, I’m so confused why that would cause such a heavy laboring sound. Like dead heading aux hydraulics. I can see it causing a settling or leak down issue? But heavy laboring why? Doesn’t the counter balance allow fluid to pass through it anyhow under certain circumstances? So why’s this little bit sneaking by causing such a drastic issue? Or is there a possible internal crack in the control valve block.. I like understanding the cause and symptoms if anyone can shed some light on the process of this hyd flow. Thanks
That looks more like a hole through the core, not a piece of metal stuck in the threads?
It appears that way, but it was just a piece of metal. I took counter balance valve to a hydraulics shop and they cleaned it up and resealed. I’m at a loss. My suspicion was correct, that little metal wasn’t the culprit (although it needed fixed anyway). Put it together, same dang symptoms. I’m hoping TVA chimes back in.. it has to be the control valve, right? Or could it be something else. I built a 2 foot hose to come right out of the control valve and right back in, bypassing entire lift cylinder hoses and everything. Up is fine, down is hard labor. Similar to when the boom is all the way up and you try to keep going. But on the way down, wholleeee wayyyy downnn. Here’s a pic of the control valve. Everything got removed, entire block got sprayed clean with brake fluid, blown out with lots of compressed air, inspected closely for cracks, and put back together carefully. Everything looked good to the naked eye, no damages or faulty springs etc. I was wondering if it’s something replaceable not working, like the end magnetic spool, but no that works fine on a bench, and when unplugged, the boom doesn’t go up or down. So must be working? Not sure what else to do, replace entire control valve without any sure visual signs of failure?