Failure site inspection and analysis:
1.Check whether the same phenomenon occurs when the idle pressure switch (working / walking) mode is switched between each other.
2.Check whether the touch idle speed is normal.
3. Check the filter: visual inspection is normal.
4. After replacing the idle pressure switch, observe whether the same phenomenon exists. Supplement: The idle speed switch is entered by the normally closed type oil pressure to increase the number of revolutions.
5. The newly replaced idle speed switch is bad, and works normally after the second replacement. Supplement: normally closed type must enter the pressure (RCV work) pressure switch to open (contact disconnection), and send a signal to the CPU (5V) to increase the engine speed The pressure switch is automatically connected to the idle speed state when the handle is in the neutral position.
6. The same phenomenon also occurs when replacing the idle pressure switch, which is mistakenly judged as CPU failure. Replace the CPU, but the failure has not been eliminated.
Failure site repair method:
Replace the new idle pressure switch to work properly.
Why does the Hitachi ZX210LC-5A excavator fail to change the speed during the work? What should be paid to the fault maintenance:
1. The idling pressure switch must first detect whether the resistance / voltage is normal.
①Measurement voltage: 5V during hydraulic operation, 0V at 0 gear.
②Measurement resistance (measure the two contact resistances of the pressure switch after removing the connector): ∞Ω when hydraulic work, 0Ω at 0 gear.
2. The idling pressure switch operates in conjunction with the walking working device, so any of the two problems cannot be converted to the idling state.
