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The grandson and I are restoring an old Craftsman lt4000 riding mower. The front grille and headlight assembly is missing. The manual specifies the replacement bulb, which is very similar to a standard 1156 automotive bulb (same bulb socket, slightly dimmer bulb). The lights are powered by an AC generator, while the battery is charged by rectified current from the same "dual" charging unit. My question is this, how can they use AC current to power a 12 volt DC bulb? Briggs & Strattonj information verifies that the light output is AC current. Being an automotive guy I can verify that the 1156 bulb is a DC bulb.

There are many lawn tractors around that use 1156 lamps powered by AC from dual and single output systems as on manual start machines that have lights. The brightness of the lamps varys with engine RPM. You can switch to battery power for the headlights/lamps if you would like providing that the regulated charging system output is enough to handle them and maintain the battery. This would require some rewiring and disconnecting the unregulated AC power to the headlights. You can leave the AC circuit disconnected but protected from shorting to itself and grounding to the machine.
Mad Mackie in CT

hudgek said:

My question is this, how can they use AC current to power a 12 volt DC bulb?

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From eHow

Auto lights are designed to operate on 12 volts DC (direct current) but can also operate on AC (alternating current). The trick is maintaining the voltage at 12 volts to keep from blowing out the bulb. Because the most common voltage of AC found is 120 volts, the voltage must be either lowered, or multiple lights must be placed in series to reduce the voltage across each light. If the the voltage remains at 120 volts after it is converted to DC, it would take 10 DC light bulbs wired in series to handle the voltage without blowing them out.

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So going by this information it is the voltage and not the type of current that matters, the voltage must be 24 volts AC initially and the 2 bulbs being in series reduces the voltage to 12 volts AC.

:smile: If it has a B&S engine. There should be two wires coming out from the under the flywheel. One of them will have a diode that changes ac to dc for the lights. The other wire is the kill wire for the mag.

If you have the two wire connector with one wire have the diode. The diode wire will be a 3 amp DC charging system to recharge the battery. The other wire will be a 4-5 amp AC system to power the lights. The above is for a non regulated charging system. If the mower has a regulator/rectifier you will have two wires that plug into the little box( regulator) and a single wire to plug into the tractors wiring harness to charge the battery, as well as power other accessories.

On the unregulated charging system engines, the headlights are AC powered. Output voltage to the bulbs will be like 14-24 volts at 60 hertz, with the engine running at 3600 rpm.

"how can they use AC current to power a 12 volt DC bulb?"

A plain bulb doesn't care if the current is AC or DC. If the current goes through the tungsten filament, it heats up the filament and emits light as long as the voltage is correct.

midnite rider said:

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Those have to be halogens!!!

Band-aid Kid said:

Those have to be halogens!!!

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Haha! :laughing: