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  1. #1
    New Member
    Join Date
    Jun 2004
    04 Kubota L3400 4wd

    Default Komatsu Excavator Safety Relay Question

    Hi Guys,

    I have a PC10 Komatsu excavator. Recently, when I turn the key on before starting, a buzzing sound started coming out. When it buzzes, the engine won't start (gets no fire). When I turn the key and hear no buzz, the engine turns over maybe once before cranking. I traced the buzz to a part in the ignition system. Its is a small square part that plugs into a plug with 5 connectors on it. The info written on it is below:

    Kokusan 12v Safety Relay SN 22029h Denki Japan.

    When the thing "flakes out," if the machine is off, it won't start. If the machine is running, it won't shut off. The problem is, I can't find any reference to this part number anywhere.

    Does anyone know where I might find a replacement, or a method to bypass this safety relay???

    Thank you for the help!

  2. #2
    New Member
    Join Date
    Mar 2008

    Default Re: Komatsu Excavator Safety Relay Question

    most komatsu equipment uses a safety relay. its function is to keep the operator from engaging the starter if the engine is running. It gets its signal from the alternator. If the engine is running and the alternator is charging, the starter motor is not allowed to engage.

    Give me the complete model number, including any - # (like, pc10-1, or -2) amd the complete serial number and i will see if i can look up the part number for the safety relay.

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