Hi everyone I have been working on a mates hitachi ex120-3 it originally had very hydraulics when cold found the p sensor wires were broken fitted a new plug and repaired checked all the wires as per the manual all ok replaced a broken sensor on the shuttle valve it was broken off once I fixed this the machine had normal function when cold but the travel speed was stuck in low . Then he got a hitachi tech up he went over the machine checked the angle sensor and a few other things then the machine went back to how it was before would not double function and some times loosing full hydraulics. He said to replace the solenoids on the pumps we done that and made no difference he has since come back and disconnected the solenoids and powered the solenoids separate it worked perfectly he checked the pump pressure 4900 psi and the relief is working properly then he checked the power going to the solenoids and it was not getting any more than 3.5 volts max at any time can anyone shed any light on this the hitachi tech is at a dead end he is thinking the harness might be faulty
Also it has had new hydraulic oil and filter no metal in the tank or filter
Welcome to HEF Ben ! Did anyone check the pump control relay (K9 I believe)? That is what supplies the voltage to the pump displacement solenoids. The controller provides the ground for those solenoids.
Ok thanks mate I will check that this weekend it could be just a faulty relay maybe has burnt contacts
Hi, Have you resolved the issue? I have almost similar problem, mine has good voltage on up solenoid but only .9V on down solenoid, i have checked relay and its good, i notice the relay continuously clicks