ym 240 battery keeps draining

[kenmac]

good way to check to see if you have a short somewhere is to , take the pos. cable off the batt. then touch the pos. cable to the battery as if you were going to connect it to the battery . if you get a small or large arc is a good indication that you have a short somewhere.

 

[ym2610]

You can also check for a open circuit or short by taking the battery cable off (can't remember positive or negative) I think negative, use a test light between the post and the cable, if it lights up with the {switch off}, you have a open circuit or short, if it don't light up, you don't have a open circuit, to test this, if you don't have a short, leave it hooked up and turn on the switch, it will light up. hope this helps someone. be careful if you take the cable loose with it running or not, a battery can blow up with a spark, it will work like he said, just be careful, wear safety glasses or face shield God only gives us one set of eyes, but thats just my opinion. good luck........Robert

 

[Keoke]

Bassfisherman, if you are showing 30 AC volts at battery then most likely the rectifier diodes are fused and acting as a solid pieces of wire. The 30 volts are peak to peak (full wave) AC or 15 plus to 15 negative coming from the alternator.
On small alternators these diodes are usually built into voltage regulator. Follow wires from alternator to find the VR unit.
These diodes usually get fused when the battery is installed backwards electrically, or when one applies a battery boost for starting in reverse polarity.
These fused diodes will also drain the battery since you now have a direct connection between the battery and alternator to ground when engine is off.

cheers,

 

[djg]

All sorts of info in the parts repair forum, troubleshooting charging system.

 

[normde2001]

Depending on where you are reading the 30vac, you may, (probably), have a bad rectifier, (inside the alternator on the YM240). the voltage is rectified to dc inside the alternator, (ac generator), and sent to the regulator where it is reduced to 13.5-14.5vdc. If you need either part, it is said that a '72 Datsun 510, (Nissan), uses the same parts, for a small % of Yanmar prices.