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PC40-7 Wiring harness fried

Discussion in 'Excavators' started by Green40, Oct 29, 2012.

  1. Green40

    Green40 Member

    Joined:
    Oct 29, 2012
    Messages:
    13
    Location:
    WA
    I am a new member here that found this site while searching for some info on my excavator. This is my first post. I am hoping to learn more about repair and maint of my equipment, and now I have a little issue that I need to resolve. I have a 96 Komatsu PC40-7 excavator I use on my property. My machine started acting strange recently. Instrument panel gauges and start-up buzzer would go on and off when I was operating it. Went to start it had a dead battery? Jumped it and heard some hissing followed by smoke. I found what looked like an auxiliary plug that had grounded out. I was able to cut it off and the machine started with no gauges. Next time I tried to start it (New battery)it was dead. Started looking at the wiring from the instrument panel towards under the seat and found it had a wire which ran all the way through the harness to a bolt near the battery that turned into an oven element. The harness has 3 large plugs located under the seat. One is melted and needless to say I need to replace the entire harness. Any thoughts our advice on where to get one ?
     
  2. Green40

    Green40 Member

    Joined:
    Oct 29, 2012
    Messages:
    13
    Location:
    WA
    180 views and no replies ? Well here is an update. I was able to repair the old harness. My dealer quoted me $1200 and approx 90 days for a replacement harness which was not exactly correct for my S/N Machine. I was able to remove the old harness (which was no fun) and replace the burnt sections. The small ground wire melted any other wire it was in contact with. I purchased a new connector for the one that was melted and reinstalled the harness. The machine works and all is well with the exception of the following.................No "warning buzzer" on start up, and no fuel or temp gage working. I used my ohm meter to verify that the warning buzzer,fuel sender and temp sender are receiving power. When the harness went out, the buzzer and gages were flickering on and off. I am wondering if they got damaged or overloaded ? Does anyone have a service manual for checking the function of the warning buzzer and temp / fuel gages ?
     
  3. Green40

    Green40 Member

    Joined:
    Oct 29, 2012
    Messages:
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    Location:
    WA
    Seems as though this is great forum, but no one has been too willing to reply sooooooooooooooo. I want to share that I was able to get all my gauges working and and now have a perfectly functioning machine. I was able to verify that the harness did provide input to the gauges (after repairing it) I removed the instrument panel and recleaned the connector, bent the tabs a bit to ensure contact and it worked! It was a simple issue, but this is the first time I have worked on something so foreign to me. I would have to say if you are patient and methodical you will succeed. I am now very good at taking this machine apart. Final cost was around $75.00 for parts and a bunch of time in my shop.
     
  4. YankeeFarmer

    YankeeFarmer Member

    Joined:
    Apr 21, 2010
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    Location:
    Connecticut, USA
    Glad things went well for you. Sometimes posts get no response because nobody has any experience with the particular issue you're dealing with.

    Jerry
     
  5. timbersalvage

    timbersalvage Member

    Joined:
    Mar 11, 2013
    Messages:
    9
    Location:
    conneticut
    I know this is 9 years old but its the only discussion relative to what im dealing with. I got a wire that must have either gotten short to ground because of mice nesting under the seat or I shorted to ground one time a few years ago when I goldberged an aftermarket fuel pump in because dealer wanted 180 for oem and I could not do it at the time. long story longer my buzzer and gauges stopped working some time ago and Im in the process of repairing the harness just as you did. Ive downloaded a shop manual and not all the colors on the diagram match the colors on my harness. is this common. the abreviations are w for white and wr for white with red stripe those 2 always line up but black on the machine is indicated by a gr in the drawings. Yellow is not listed at all in the drawing and is used in the harness in a few spots. Is this typical?
     
  6. John C.

    John C. Senior Member

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    Occupation:
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    For some reason I seem to recall the wiring designations were in french. Some dim dark place in what is left of my mind just floated something about a problem with blue and black colors plus something about yellow in the Komatsu language of wiring harnesses. It will probably float up the rest of it by Sunday, maybe.
     
  7. timbersalvage

    timbersalvage Member

    Joined:
    Mar 11, 2013
    Messages:
    9
    Location:
    conneticut
    It wont start with keyswitch. Ive checked the switch and the starter both are good . the what they call safety relay is not sending juice and I'm pretty sure I've zeroed in as being one of the problems, but its 400 bucks. can I retro fit some thing else? . its got some kind of sealed box with 4 wires coming out of it It says Hitachi AST1-11 on it. Thats too much geech I cant afford
     
  8. timbersalvage

    timbersalvage Member

    Joined:
    Mar 11, 2013
    Messages:
    9
    Location:
    conneticut
    Does anyone know where I might get a junkyard controller for Komatsu pc40 r-8 its a Hitachi AST1-11 the Komatsu part # is YM129136-77100 its common among yanmar powered equip
     
  9. skata

    skata Senior Member

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    Location:
    midwest