Komatsu "Four" (safety) System

Hi,read previous posts ,all info is in them regard bridging or bypassing system ,but as i said in my last post if your eye ,hand ,brain coordination is not good ,the bucket will kiss you in the cab U bridge the hoses that go in the side of the valve that go in 1 side and come out the other side opposite each other together on the long side of the valve ,other pipes just blank off.bridge old fittings on valve with old hose to keep rubbish out ,weeping oil

postmortem_42 said: Hey guys, new to this forum and just purchased a used PC28UU-2, S/N 10274. I am having similar issues to the above safety feature with the momentary override switch wired to always on. I have looked under my floorplate for a valve block under right foot but this appears to not be what is being described. However, under my left foot and to the rear is a valve block with 4 solenoids with 3 smaller/1 larger hydraulic lines going into to top and some small/large ones exiting side. If this is it, I can't really tell which lines to bridge and need some help in doing so. Any help would be greatly appreciated as the arm moves very slow, but all else is ok. Thanks Click to expand... On our pc28uu-2 someone before us unhooked the solenoids, defeating the position sensors. Not sure if they did anything inside the valve block, but it appears to be undisturbed. An undesirable side effect is the lock lever doesn't work either. Wiring and Hydraulic diagrams seem impossible to find for this machine.

Dont bridge the fittings on PC28UU as stated, it overpressurizes the pilot control system and blows hoses. There has to be some internal bypass passages in the aluminum valve block that relieves pressure. Trust me

Mike_27, when you say unhooked, just unwired all four?

postmortem_42 said: Mike_27, when you say unhooked, just unwired all four? Click to expand... yup, they are just unplugged.

Mike_27 said: On our pc28uu-2 someone before us unhooked the solenoids, defeating the position sensors. Not sure if they did anything inside the valve block, but it appears to be undisturbed. An undesirable side effect is the lock lever doesn't work either. Wiring and Hydraulic diagrams seem impossible to find for this machine. Click to expand... Mike_27 said: Mike_27 said: yup, they are just unplugged. Click to expand... Thanks for reply. Do you happen to have a service or parts manual for the UU-2? Click to expand...

John C. said: The system you describe was pretty common on gray market machines some years ago. I've seen plenty of them and there are differences between model years and machine models. PM me your email address and I'll send you what the info I have. The systems were an add on and I don't believe they are supported by Komatsu. Click to expand... John Do you have any information on PC-28 UU-2 system? i am looking for exploded view of the aluminum valve block the pilot hoses and solenoids go into? Thanks

Here's a part book, the EPC Valve is on page 313. I've looked for the service manual for a few years without any luck.

Thanks!!!!!

You cant bypass the aluminum valve body as others state. This valve body that solenoids are connected to regulates pressure from the PCP and bypassing will either burn out your PCP if it lasts that long or blow hoses on both the feed and return sides going to your pilot controls. I learned more about this system than I wanted after messing with it. The solenoids get 12V usually, and when the potentiometer hits a certain setting, it will shut down solenoids (one for boom, one for stick and one for offset, the fourth solenoid holds open the feed from the PCP and is switched on with key, other solenoids powered by computer or by momentary switch in ON position). You have 2 choices, either wire up all 4 solenoids with 12V full time or modify your plungers on solenoids to push spool valves to open position when bolted in place. There should be no slower operation of controls, unless somehow the computer is regulating voltage to solenoids causing them to not plunge out all the way. PM me if you need more information.

Hi Postmortem_42 have you tried to keep your dead man work with the 12 v feed to all 4 solenoids ? if so any down side to this ? and what size cable are you using to power up all 4 solenoids ?

sorry have you it fused and possible diode in the line also ?

no diodes, no fuses. using the power from the override switch at 12V and 16AWG wire. No real current running through them. There is no downside to powering all the time as that is the normal way they work if the safety system was operational.

Thank a mill for the advise I will try it out this weekend, will the dead man lever work the same or would you advise connecting and second switch for ground in parallel to original one, for the safety aspect for getting in and out

mine does not have a safety lever, it is a UU2 SN 1264,but no "dead man" lever. I believe that if you run a toggle to solenoid no.1 (one of the smaller ones on end that controls incoming pilot hose pressure) you can kill the controls, hence a dead man. Killing 12V to that solenoid will make controls dead, but you will still have tracks and dozer blade as these are linkage.

correction SN# 10274

Have you disconnected the controller unit to stop the light flashing and buzzer noise , can it be as simple as a fuse ?

I have two buzzers, I can simply disconnect the plugs to shut them up. I am installing oil pressure and WT gauges and will ultimately delete the dashboard. The flashing red light with Japanese writing is annoying....

thanks very much for your help on this hope get it done over the next few days

good luck, you will get it figured out