Hi guys i'm new to the forum I have a Hitachi EX 120–3 I have had this machine for approximately three years when I bought it it had an issue A bad wire going to the pump control relay I had a mechanic come out and he jumped a wire from the windshield wiper relay two the pump control relayand it fixed the problem (I use this machine on my small farm it doesn't get used every day) from time to time when I start the machine the throttle didn't seem to run at the same rpm sometimes a little faster or slower when I started it up but it ran fine I was using it this past week when an it idle down and wouldn't respond to change in the mode (I.L.E.or P.to speed the motor up so I did some reading in the shop manual found out pump control relay and EC motor relay get power from the same fuse The wire that was feeding the pump control relay from the windshield wiper relay was loose I could shake the harness to make it lose powerso I ran a new wire from the fuse box to the pump control relay and EC motor relay it started after that but would only idol very slow so I did some more reading and check the voltage at the EC motor sensor with the 8 mm bolt holding the T link in the idle position I was only getting 1.6 Volts I adjusted the sensor to 2.5 volts it started and ran fine I turn the key off when I tried to start it it did the same thing again I don't very slow and started I check the voltage again the voltage was low set it back to 2.5 it started and ran fine cutting off again and it doesn't same thing it won't hold that voltage any help would be appreciated sorry for the post being so long just trying to get everything out there to you guys William
sounds like computer reset it self .......beside the fuse panel there is a toggle switch now pay attenetion to the position its in ......then click it up turn key switch on count to 5 turn key switch off and wait put toggle switch back in position it was in when you first saw it Crank engine and see how throttle works if it doesn't idle right get a 6mm allen wrench and open throttle dial wide open take 6 mm allen wrench and go to back of excavator open panel where hydraulic pump is and find throttle cable and small motor that controls it and you will see a lever un lossen allen screw and move cable till its wide open tighten back and when you turn dial down it will be back to normal ....I had one do this 4 times and the grease in that motor was hard as rocks and gear in there is rubber so it gets out of time
I looked around the fuse box there's no switch .there's a slot in the fuse box looks like there could have been at one time .if I adjust the linkage to make it run right I can go through Idol low medium or high it will work fine when I turn the key off and started back up sometimes it work right most of the time it idled real slow slow enough where it won't start on the lowest setting i'm about ready to put a manual problem it but I would like to be able to fix it right
Anyone know where the wires to the learn switch come from , mine was taken out by a “ mechanic “ and now can’t teach ec motor Thanks