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starter gen amperage

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Hi. A few years ago, I repowered my 917 AC with a 16 Hp briggs single with a starter generator. The motor was previously used on a grain auger, I believe. The motor had been converted to battery-coil ignition.

When blowing snow tonight, I noticed the engine would stumble at WOT, whenever I would turn the lights on. I ran without the lights, and all was well.

I assume the starter generator doesn't produce enough amperage for the lights and the coil. Does this sound right? The lights are the stock round lights in the 917 hood. Don't know what the wattage is on those, but they are pretty bright.

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The SG is a nominal 10-15 amp generator and that should handle two lights and an automotive ignition coil real easy. I would meter your battery to check its condition and if that checks out, look for questionable wiring.

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I agree with Bob. Sounds like the voltage is dropping at the ignition switch when the lights are turned on. The coil current draw is relatively low compared to the light draw, so I suspect poor or dirty contacts on the ignition switch, circuit breaker, or fuse. Could also be a bad wire (internally broken with only a few wire strands still intact) causing the resistance at the higher draw.

In addition to the voltage check at the battery, and assuming the battery checks OK, I'd check the voltage at the lights both on and off. The voltage should be 12v in "off", and not much lower in "on"; if not, then then there's definitely something in the current path with high resistance.

PS - I'd do the checks without the tractor running. The battery circuit should be able to provide power to both the coil and lights without a problem for some time before the battery runs out of juice.

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