125 Charging System

[rammerjammer05]

1258v7b.Just installed a volt meter today at my dash. When I checked to see if the charging system was working I was only getting around 13 volts with the motor running at about 1/4 throttle (no tach). Thought that this was a little low on the discharge from the stator so I checked the stator per the test procedure. Everything checks out ok. Unhooked the two AC wires that come off the stator and checked them and I'm getting around 20-25 volts(AC). Hooked everything back up to the rectifier and still only 13 volts (at the battery). Unhooked the red wire from the rectifier and getting around 16volts (positive from meter to ac negitive from meter to ac). Noticed that the red positive wire that hooks up to the rectifier has 12volts going to it while the engine isn't running. Traced the wire to the (B) terminal on the ignition switch. Is this correct for the red positive wire to the rectifier to always have 12 volts going to it. I was under the impression that this wire was for sending the charge that the stator puts off back to the battery side of the starter solinode and then back to the battery. Can't figure out how if there is power going to the rectifier then how is the current reversed back to the battery. Do I have something hooked up wrong. Never really noticed how many volts were being discharged from my stator till now. I have also just replaced the rectifier and tested it and its ok. Checking stator discharge at the rectifier and the battery with ohms meter.

 

[Jiggz]

Re: 125 Charging System

You did the right voltage check on the AC side of the rectifier which are the two wires coming out off the stator. Now you should have checked the DC side of the rectifier which should ready higher than your battery terminal voltage. 13V from the DC side of the rectifier is a little low and this could be that the rectifier is partially bad. It could be one of the diodes is already open or not working. As for the red wire from the DC side of the rectifier, yes, it's always hot but doesn't have any load connected to it. And yes, with the DC output of the rectifier having higher voltage it will charge you battery. I see you already replaced the rectifier. So now do the following: Check DC voltage off the rectifier (red wire and balck-ground wire) with the engine off. This is your battery terminal voltage. Now do the same thing with the engine running. This is your charging voltage at idle which is usually 13~14 volts. Rev the engine up to 1500 RPM and you should see the charging voltage go up a notch.

 

[fucawi]

Re: 125 Charging System

if the battery is run down it will hold the output at the 13v that you are quoting ...you need a couple of hours + at reasonable rpm to bring the battery up ...quickest way is to charge it with a mains charger over night and go for a run next day ..that will tell you what the voltage peaks at....alt output quite small takes a long time to charge it if its well down