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engine run power feed

  1. Need "engine running" power feed!

    Gauges, Electronics and Wiring.
    I need a power feed that only works when the engine is running. I need it to control a relay for trailer charging. In the past, I have used an oil pressure switch that closes when the oil pressure rises. It would be easier to tap into a feed in the fuse box, but I don't know which one would...