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Need MF12 charging advice

1034 Views 3 Replies 2 Participants Last post by  JimC_Vt, 
M
I just repatriated my old MF12 and it is running great but appears to have some charging issues. I am hoping some of you guys will part with some wisdom and save me some time in the troubleshooting process.

When I started I found a fuse in the black wire that runs from the regulator to the ignition switch (single connector, not in the Molex) was missing. I put in an 8A fuse and the charge gauge shows a tiny charge at speed, just off the zero mark.

Brand new battery.

Putting a volt meter on the battery stopped voltage is 12.4 . Running WOT the voltage is actually .2 less.

If I put the volt meter in the regulator side of the disconnected above mentioned fuse holder it reads 19+ volts with the engine running at speed.

My first thoughts are to clean connections and grounds, and to jumper past the ignition switch if cleaning is non-productive.

Any advice would be appreciated.

:banghead3
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JimC_Vt
A new battery should be ~13.8 volts sitting (2.3volts) per cell....The voltage from the engine is A/C....so I assume your getting that ,then thru the VR,and it's rectified to DC voltage !14.0 to 14.5 volts DC .....with that said ,with the engine running ,and your loosing voltage ,I would say your diode of VR is bad ....BUT all the connections must be clean,so check them all ,AND the grounds are very inportant so be sure all the grounds are touching bare metal....Good luck ,Jim
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JimC_Vt said:
A new battery should be ~13.8 volts sitting (2.3volts) per cell....The voltage from the engine is A/C....so I assume your getting that ,then thru the VR,and it's rectified to DC voltage !14.0 to 14.5 volts DC .....with that said ,with the engine running ,and your loosing voltage ,I would say your diode of VR is bad ....BUT all the connections must be clean,so check them all ,AND the grounds are very inportant so be sure all the grounds are touching bare metal....Good luck ,Jim
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Well, I cleaned all the contacts and all is good. I did learn some things along the way. The ignition on the tractor is a magneto ignition. I learned that on this tractor if you have the ignition switch out of the dash and are holding it in your hand while the tractor is running it will zap you pretty good. I also learned that the ignition switch uses the dash as a ground connection so that if the ignition switch is not hooked to the dash you cannot shut the running motor off! Even disconnecting the switch completely and disconnecting the battery left the magneto engine running happily! Let me tell you there was some head scratching going on there.

Thanks to all for your help and advice!
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JimC_Vt
Hurts like ****,kinda and kinda surprises you real well ....it's amazing what high voltage will do to find a ground ...your luck theres not a lot of amps to really put you in a spin....Good Luck,Jim
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