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Komatsu PC90 Overheating Issue

Discussion in 'Excavators' started by Bobbyleeb, Dec 6, 2019.

  1. John C.

    John C. Senior Member

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    Correct. Your photo of the monitor in your machine only shows the S and L power modes. The machines with a machine control computer will show HO, SO, LO and FO.
     
  2. LACHAU

    LACHAU Senior Member

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    Sorry...so sorry Sir; but I should inform that PC90-1 has 02 controllers : one for PUMP and the other for Engine throttle!!!

    PC90 Pump Control (1).png

    PC90 Pump Control (2).png

    PC90-1 Electric Circuit.png

    PC90-1 Hydraulic Circuit.png
     
  3. LACHAU

    LACHAU Senior Member

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    Attached files are Hydraulic and Electric Circuit diagram in PDF format for more convenience reference.

     

    Attached Files:

  4. LACHAU

    LACHAU Senior Member

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    The other is ENGINE controller.

    PC90-1 Electric Circuit Diagram2.png
     
  5. John C.

    John C. Senior Member

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    It does not actively stroke and de-stroke the pumps as the engine load is increased or decreased. Do you see a speed sensor in the schematic? We used to see the same thing in the PW90 machines. The power set switch only has two positions, light load or full load. The TVC solenoid pressure is preset so that the engine can't be overloaded. There are no diodes to indicate faults in the systems. My thought process is the someone turned the screw in a bit or there is something wrong with the solenoid valve. It can probably be tested by running a boom up cycle time. If you are getting boom up cycles at 3.5 seconds or less, the pumps are overloading the engine.
    Thanks for the schematic! I love that it can be blown up for an easier read.
     
    LACHAU likes this.
  6. LACHAU

    LACHAU Senior Member

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    In this regard, you're right John! But PC90-1 hydraulic control system also has some other functions.

    PC90 CONTROL SYSTEM (1).png

    PC90 CONTROL SYSTEM (2).png
     
  7. LACHAU

    LACHAU Senior Member

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    We may go too far!!! Back to main subject is "OVERHEAT".
    Bobby, Could you inform us about MAX Hydraulic pressure??

    1. A lot of excavator's overheat due to hydraulic pressure set too low!!!
    2. Does the machine get OVER-LOAD at heavy load (Engine speed drop down)???