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Question about a Motorola Alternator


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#1 MNGB ONLINE  

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Posted October 15, 2017 - 11:36 AM

Hi all, I looked and did not find a sub-forum on alternator/generators so I'm asking here.

I'm installing a Motorola alternator on the John Deere LA I know how to wire it the question I have is this alternator / voltage regulator use a 12Volt feed from the ignition switch to excite it well the LA has a magneto so there is no 12V from the ignition switch I've checked the alternator and it works if I use a jumper from the battery connection to the red voltage regulator wire the alternator comes on line and works good I know I could put an on/off switch on the hood and turn it on and off but I'm wondering can I just install a permanent jumper from the battery terminal to the red wire terminal??



#2 olcowhand ONLINE  

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Posted October 15, 2017 - 11:43 AM

If it's the excitation wire, you need the connection broken when off or it will drain your battery.


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#3 jimmy G ONLINE  

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Posted October 15, 2017 - 11:47 AM

I'm thinking the starter feed might work, should work same as key i would think, only on when starting

Edited by jimmy G, October 15, 2017 - 12:02 PM.

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#4 MNGB ONLINE  

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Posted October 15, 2017 - 12:15 PM

Thanks for the replies I was kind of afraid of that, no solenoid on this tractor pretty simple mechanical starter switch looking like a switch is needed.



#5 jimmy G ONLINE  

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Posted October 15, 2017 - 12:20 PM

Dang it, you beat to my correction lol
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#6 MNGB ONLINE  

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Posted October 15, 2017 - 12:54 PM

Thanks guys, I got an idea from another source, use a garden tractor type switch that's for a magneto that way I'll have a mag switch and the 12 volt feed needed, and this tractor needs a mag switch as there is not one on it at the present.


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#7 KennyP ONLINE  

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Posted October 15, 2017 - 12:59 PM

Thanks guys, I got an idea from another source, use a garden tractor type switch that's for a magneto that way I'll have a mag switch and the 12 volt feed needed, and this tractor needs a mag switch as there is not one on it at the present.

That should work! That would 'excite' the alternator and give a connection back to the battery for charging. Run a good sized wire though.


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#8 MNGB ONLINE  

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Posted October 15, 2017 - 01:06 PM

Thanks just got another idea could use an oil pressure switch that is on with pressure and off with no pressure.


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#9 Genem OFFLINE  

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Posted October 15, 2017 - 01:34 PM

I wonder if an the oil pressure switch would be made with a current rating to handle the current that the alternator may draw or is it a constant exciter draw only. Genem
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#10 MNGB ONLINE  

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Posted October 15, 2017 - 01:54 PM

Hi Genem Hobbs make a good switch, but I'm pretty sure I'll go with the mag switch as the tractor needs a mag switch and that would neatly do all that is needed.



#11 glgrumpy OFFLINE  

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Posted October 15, 2017 - 05:45 PM

Big tractor guys use a bulb or resistor in wire so it won't feed back when off and drain battery. Not sure why that works myself. OR, can just put in on/off switch for charging, had to do that on one of my MM's when couldn't seem to get foreign alt to work on it any other way.  Maybe that was a Diode, not resistor in the wire, makes more sense.


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#12 olcowhand ONLINE  

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Posted October 15, 2017 - 06:11 PM

Thanks just got another idea could use an oil pressure switch that is on with pressure and off with no pressure.

That's how some of my full size Massey's control excitation.


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#13 MNGB ONLINE  

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Posted October 16, 2017 - 01:08 PM

Hi all, well this morning I temp wired up a GT mag switch and it worked perfect, turn the key to on and started the engine and the alternator was putting out 14 vdc and when the switch was tuened to off the engine stopped just like in the movies all is good, also worked on pounding out 3 / 4 dents in the hood and bending back the metal the was cut and bent in the starter access opening now just need to weld or braze the cuts.


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