QuestionQUESTION: Hello, I have a 12hp Briggs and Stratton engine on a Murray riding lawn mower. The battery loses power when not in operation, or isn't charging while in operation, or maybe both, but it always runs good when we have a good battery charge to start it, but I have to charge the battery nearly every time we want to use it. While machine is running, and the positive cable is then disconnected, should there be amps at that cable, to charge it? Should there be amps to the wire going to the alternator when the machine is not running? Thanks for any help you can give me.
ANSWER: Seeing that it will run OK you have a diode out. The diode is in the rectifier/regulator or bridge rectifier depending on which system you have.
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QUESTION: I have a black lead from the engine (stator)with a connector, with no diode, and then that wire goes to the ignition switch. There is no rectifier/regulator that I can find. I purchased the lawn mower used - could it be that it was removed? Should I add a diode or rectifier/regulator? The yellow wire from the magneto has a small amperage of roughly 0.1mA at low throttle while engine is running. That wire also goes directly to the the ignition switch. Might the magneto be operating at too low of amperage and not charging battery enough?
Thanks again so much for your assistance. It's greatly appreciated.
ANSWER: The yellow wire coming a from the ignition coil is a kill wire and will ground when you turn the key switch off. There should be to other wires coming out from under the flywheel they probably both go to connector plug usually one will be read in one will be black. The red one should have a diode in line and it's no more than a bump in the wire. One of the wires coming from that connector goes directly to the key switch the other when usually goes to the seat switch. Seeing that everything on the tractor is DC the wire coming from the engine with a diode in only let DC out. All engines only produce AC. The key switch then moves that current to the proper connector in the key switch to start run or kill if the diode is out nothing should work the battery slowly die. Remember the battery should be charged to 12.6 V DC to be able to start this engine cold. The 12.6 V comes from six plates in the battery each having 2.2 V in them when fully charged. This information is help you out.
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QUESTION: Thanks for your help. It's obvious my engine is not wired properly. I have only the black wire coming from the stator, without the diode. According to the wiring explanation from B&S, that would be an AC only system (as you explained), with only 1 headlight, and no battery recharge capability. My question I guess is, what can I do to make this work? Purchase a dual circuit stator with red and black wires, for a 3 amp DC charge, and 14 volts for AC lighting? Thanks again.
AnswerI think your system needs a bridge rectifier will convert the AC voltage into DC voltage coming off a will charge the battery the other lead coming off it would go to the head lights and the fourth through the safety system most of this will go through the key switch first. If you have the exact model number and serial number of your tractor you should be able to go online someplace and find a manual for it. It will more than likely not be no charge. It's in Portland at this point to see if schematic otherwise you could try many different connections and end up blowing fuses or damaging your ignition coils. Briggs & Stratton offered different bridge rectifier's and regulator rectifier's with their engines. We will need to know which one goes with your tractor wirings system. I believe Marie of Ohio was bought out of bankruptcy by Briggs & Stratton a Briggs & Stratton distributor may have old manuals on microfiche but you will need your model number and serial number of the tractor. Best of luck on your continuing project.
