KOMATSU PC75UU-2

[Mike59]

Hi all,
Have got a problem with my digger - Komatsu PC75UU-2. No boom up & have finally diagnosed it down to the boom raise solenoid. Bare wires which have obviously shorted it out. Problem now is trying to get hold of one - Komatsu UK say no one in the UK is stocking any & said the price listed is £ 615 which is madness for a bit that fits in the palm of your hand ! Currently making enquiries abroad for an aftermarket one. Just wondering if any of you clever people have any ideas of a workaround ? Also wondering if the old unit would be repairable by a specialist ?, although it seems a completely sealed unit & I wouldn't know how to get into it. The original Komatsu part no. is 21W-60-22180

 

[V8Druid]

Hi all,
Have got a problem with my digger - Komatsu PC75UU-2. No boom up & have finally diagnosed it down to the boom raise solenoid. Bare wires which have obviously shorted it out. Problem now is trying to get hold of one - Komatsu UK say no one in the UK is stocking any & said the price listed is £ 615 which is madness for a bit that fits in the palm of your hand ! Currently making enquiries abroad for an aftermarket one. Just wondering if any of you clever people have any ideas of a workaround ? Also wondering if the old unit would be repairable by a specialist ?, although it seems a completely sealed unit & I wouldn't know how to get into it. The original Komatsu part no. is 21W-60-22180

surely this isn't an electro servo control machine ????? one of those 'grey import' knuckle off set boom jobs, isn't it ... and quite an age ..... any pix?

 

[craig]

surely this isn't an electro servo control machine ????? one of those 'grey import' knuckle off set boom jobs, isn't it ... and quite an age ..... any pix?

Didn't you put a link up for a solenoid supplier a while back?

 

[V8Druid]

Didn't you put a link up for a solenoid supplier a while back?

yeh I did but damned if i can recall where it is ..... big range they had too .... see if i can recall where

found this in me bookmarks https://www.solenoid-valve.world/category/4243

 

[craig]

yeh I did but damned if i can recall where it is ..... big range they had too .... see if i can recall where

found this in me bookmarks https://www.solenoid-valve.world/category/4243

That`s the one.

 

[Alan caddy]

Is machine fitted with a height limiter, as if that's gone fault will stop boom up, usually a solenoid that cuts the servo supply which can usually be bypassed

 

[V8Druid]

Is machine fitted with a height limiter, as if that's gone fault will stop boom up, usually a solenoid that cuts the servo supply which can usually be bypassed

that would certainly explain any level of electro servo control .... some pix'd certainly be helpful

 

[JD450A]

Where in Devon are you

 

[T whiting]

Is machine fitted with a height limiter, as if that's gone fault will stop boom up, usually a solenoid that cuts the servo supply which can usually be bypassed

That's what happened to my duck on a Saturday shift I bypassed it by joining the hoses and capping the drain line.

Is it just the cap on the solenoid that's got rubbed wires? You can get replacement caps do you have any pictures?

 

[Alan caddy]

Happened to me on hydro shut down, tracked machine onto low loader got to other end no lift on machine, put servo pipe straight onto valve block and took t piece out of return line to get mobile quickly

 

[Mike59]

Many thanks for your replies guys. Well yes, it is an old machine - must be somewhere around late 1990's ? We reckon it's definitely the solenoid, as after checking/repairing loads of loom, we realised we'd lost the positive feed to the solenoid. We introduced a new feed from a separate battery & hey presto we had boom up. Unfortunately that was obviously enough to finish off the solenoid - when we took it out, it was soaked in oil & dirt + both wires were bare at exactly the point they pass into the metal body of the thing, so must have shorted out. I've now managed to buy one with the right part no. from Lithuania - aftermarket of course, but a fraction of Komatsu's ridiculous quote ! Even if by a stroke of bad luck, it doesn't fix the problem, we couldn't have left it like that. In answer to the height restrictor question, I assume those are the potentiometers ? They don't work & appear to have been disconnected long ago. According to my friend (the operator) the moniter has been showing error 51 or 42 for the whole time we've had the machine, but it doesn't stop it from functioning. The wiring loom is in a mess, we've tidied it up a lot, but would probably benefit from a complete rewire - just not cost effective on an old machine like ours though I guess. I've got a full workshop manual for the machine & that seemed to indicate that the ECU controller behind the seat would shut down the function indicated by the error code ? but that doesn't appeared to have happened in our case, so I'm a bit confused. The wiring appears to have been messed around with a lot over the years, so I expect some stuff has been bypassed. We won't be back over at the machine until later in the week, but I'll take a few pics & let you know how things went (well hopefully !) & it may just be useful to someone in the future.

 

[Mike59]

Our old Komatsu PC75

 

[Alan caddy]

You should be able to by pass the solenoid valve and put the pipes straight onto the valve block and do away with the bad wiring issue, it's usually added into the pilot feed to spool block

 

[Mike59]

Excellent, thanks for that. I had wondered if that was possible, but didn't want to risk getting into even more problems !

 

[Alan caddy]

I would say taking it out of the system will save you a lot of future problems if wiring on machine is suspect

 

[Mike59]

That's what happened to my duck on a Saturday shift I bypassed it by joining the hoses and capping the drain line.

Is it just the cap on the solenoid that's got rubbed wires? You can get replacement caps do you have any pictures?

Completely sealed unit (as per stock photo) - just can't get into it.

 

[Mike59]

I would say taking it out of the system will save you a lot of future problems if wiring on machine is suspect

Yes, I reckon that will be the way to go. We had another wire (blue/white) which was burnt out & had completely melted insulation. According to the wiring diagram it runs between ACC on ignition & the alternator - we've replaced it but have yet to find out what it was doing, as everything else is working okay & batteries are charging fine. Can't help thinking they borrowed this wire for the solenoid feed & the 2 problems are connected. Also would have hoped it was protected by a fuse which should have blown ? Wondered if vermin may also have nibbled at the loom, as we have had problems with mice in the past

 

[ErnestCapher]

you can find Komatsu Manual, from this site i bought once, machinecatalogic.com/komatsu-pdf