HEQ members. Have a new to me Hitachi ex 120-2 that has arrived. I started a listing below of repair support questions from the forum experts here... Prior owner said Hitachi was diagnosed as needing a new computer and possible main pump rebuild, due to operating a little weak. Seems to me to operate pretty well except for the frozen pins in tracks, it binds so hard machine stops, so first trying to free those up. Also, where is the diagnostic plug to short the wires? 1. Smaller computer on top has no lights on it, looking for wiring diagram help and fuse support ec. 2. Has manual throttle, works good, seems to be from the above computer being dead, is there voltage to test stepper motor? 3. Has a manual temperature gauge, maybe the same as the throttle above from computer dead 3. Third light down on display console lights up once RPMs go up. looks like a flow-down arrow indicator. 4. Pretty good leaking bucket cylinder. 5. Track chain pins are frozen bad, binds up and stops machine from tracking. Guessing powerwash and then Kroil to try and free?
Behind the right arm rest. Only read the PVC (Pump and Valve Controller) for codes, not the EC (Engine Controller), which sounds dead anyway. One on top is the Engine Controller (EC). The one on the bottom is the Pump and Valve Controller (PVC). Voltage comes from 1A fuses F2 (second up from the bottom left) to pins 27 and 34 of the EC and F5 (5th one down on the left) to pins 27 and 39 of the EC. Grounds are pins 25 and 38 of the EC. You need to get the EC working before worrying about the stepper motor. Post a picture of this?
@mg2361 , Thanks will give that a try to the below and report back.
Fueses are good, controller seems dead. Does anyone know what PN matches the Hitachi Engine Controller? It has on it a sticker, EX120 03N10, 0200 022745A. Also, machine SN# 12N - 30987
Has the voltage and grounds been checked with a meter at the controller? Performed with the controller plugged in, key on and carefully backprobed at the terminals I mentioned?
@mg2361 , Thanks for the above wire locations. Was awaiting a tech manual to ensure I knew when looking at the EC plug, where to probe for pins to check voltage. Is it assumed voltage should be 12v or 5v at the above pin locations? Also, looking at the plug while plugged into EC, pin 27 is the upper left?
Sorry, error on my part. Voltage to pins 26 and 39, and pins 24 and 37 of the engine controller. 24 volts Not sure. I don't have the connector diagram. 26 and 39 should be red/black. 24 and 37 should be red/white. Post a clear close up picture of the plug connected to the ECU.
One addition to the above while I troubleshoot. The batteries get weak etc. if not cranked up every few days. Guessing a draw somewhere, any thoughts on testing for that?
Digital amp meter between the battery negative cable and battery negative post. With the key off you should have 0.025 amps or less. When the meter is first connected it might spike to 0.3 or more for a few seconds and then come back down. That is normal. I'm guessing 0.1-0.2 or more if your battery is draining that fast. if it is too high then you can either test voltage drop "across" each fuse in which there should be none. Any voltage drop across a fuse with the key off (and battery connected) is too much. Or you can just pull fuses one at a time and when the meter drops to 0.2 or less then you found the problem circuit.
@mg2361 , The pins for red/black and red/white, as well pink(EC relay) all had 23.75vdc.
The grounds? Measure them as well. They should be 0.100V or less. Pins 25 and 38 (black wires).
All 4 grounds checked out less than 0.051V and less.
Did you check for codes in the PVC?
The below the Dr. ex plug? I shorted right side, then left side, PVC never flashed in code mode.
Did you short the two shown below together, then key on?
@mg2361 , yes, did short the above two wires. When turning key on, just the normal PVC light blink occurs.
Then there are no codes in the PVC.
Would there be a potential process of elimination to check other sensors/circuits? As if the EC is dead, I would not want to risk buying a new one and fry it at plug-in.
If I am not mistaken, the only things on the EC controller are the EC motor, EC motor feedback (position sensor) and the engine speed sensor. The EC motor drive circuit would certainly provide enough current if shorted internally or it's wiring shorted to ground to fry a driver. On the PVC a shorted 5 volt reference can turn the light out, so I would also check the 5 volt reference circuit as well. Backprobe the EC motor position wire (terminal #1, Blue/white wire??) 5 volt reference wire and see if there is 5 volts present. If not, then while still backprobed, key off, unplug the sensor, then key on. See if the 5 volts shows up. Important to note that plugging and unplugging the EC motor drive circuit with the key on can ruin a controller. I PM'd you.