Question on wiring a Motorola alternator

MNGB

Well-known Member
Hi all, I'm installing a Motorola alternator on the John Deere LA (Motorola is from a mid 60's AMC) must have left my model numb er note at the shop anyway, I know haw to wire the alternator this alternator requires a 12 VDC feed from the ignition switch to excite it but the LA has a magneto so there is no 12 VDC available to the ignition switch I know I can install a seperate switch and turn it on/off but my question is can I just attach a jumpwer wire from the alternator battery terminal to the red VR wire to do the same and leave it permanently on (12 volts on that wire all the time??
GB in MN
 
Don't think it will work, the alt will be energized the whole time(running or not) and will kill the battery. single wire delco
would be my choice
 
Thanks form the information, Delco is out to big and I'm trying to save some money have this perfectly good Motorola.
GB in MN
 
MSM has it correct in that you need to break the 12 volt supply or the regulator will run the battery down. An alternator with a self exciting regulator would not need any exciting current. That is what a single wire alternator usually is.

Truthfully the Motorola are not the best to use in that they usually are set up for an external regulator. This makes them harder to wire. I also think the Delco's of the same vintage are more rugged and much cheaper to buy/repair.
 
There are other Delcos other than the 10SI frame that are smaller.

I do not know of any Motorola that has a self exciting regulator. So you will have to have a switch.

One idea is to get a switch that has one terminal grounded when off. You can then hook that terminal to your magneto for kill and one of the other terminals for the regulator supply. There are lawn mower switched that do this so that type of switch is not hard to find.
 
Yup, go with the Delco and put your old Rambler back on the road where it belongs. Some guy'll see it and
want to buy it which, if your lucky, will pay for the Delco alternator .....
 
(quoted from post at 10:56:02 10/15/17) There are other Delcos other than the 10SI frame that are smaller.

I do not know of any Motorola that has a self exciting regulator. So you will have to have a switch.

One idea is to get a switch that has one terminal grounded when off. You can then hook that terminal to your magneto for kill and one of the other terminals for the regulator supply. There are lawn mower switched that do this so that type of switch is not hard to find.
Thanks JD your switch idea that will work, I know there are small alternators if going that way I would use a Denso one wire its smallenogh to fit up the hood and simple to install provided the mount will work, and yes there is a Motorola self exciting VR available but its cost is about $40.00 and a Denso Alternator is less than $70.00. Thanks for the replies.
 
NOT at all hard to do IF you have the basic connection diagram for the alternator and regulator.

Simply install a normally open/closes about 4 psi oil pressure switch (tee into the gauge fitting, if necessary) to cut the battery power to the VR when the engine stops.

What type of regulator do you have...

<img src = "http://theamcpages.com/images/electric/charging-sys/regulators_TVR12AM18.jpg">

<img src = "http://theamcforum.com/forum/uploads/3/alternators-regulators-6.jpg">
 
Thanks Bob, I have the top one the TVR unit and yes you ideal will work also. I'm liking the ideas and possibilities
GB in MN
 
Hi all, well this morning I did a temp wire up using a GT mag switch started the engine and it worked perfectly 14 VDC going to the battery and when the switch was turned to off the engine stopped just like in the movies all was good.
 
Hi well the Motorola alternator installation is completed fits under the hood nicely got it wired as was suggested I used a GT mag switch for an ignition switch and to excite the alternator and it all works as it should started the engine alternator went on line 14 VDC ammeter indicated a + charge trned the mag switch to off and the engine stopped, happy days are here and the LA is coming along nice.
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