Wiring help

BigTone

Member
I'm going to rewire the A this wknd I hope,
alternator and magneto with no lights right
now. I'm basically going to rewire like it
is right now just have a couple questions.
They are using what looks like 14 or 16
gauge wire for everything, my M used 10 and
14, should I use a specific gauge for this
or will 14 across the board work ? Also,
it has a toggle switch hooked up to a fuse
and in line with the alternator I believe,
i want to add a key instead of toggle dich,
should I put it line between the plunger
switch to the magneto instead? Thanks
Anthony
 
If you connect your magneto to the 12V power you will fry it. Magnetos do not require electrical power. Leave the magneto wiring alone.

The push button is for exciting the alternator.

Here's the wiring diagram you should follow:

v6097.jpg
 
I would use 10 ga. from alternator output to ammeter to starter solenoid/switch. 14 ok for the rest.

If using common Delco internal regulated alternator, exciter wire from switch through fuse should go to #1 edge pin. Rather than toggle or key switch I would use a momentary push switch. You only need a momentary voltage to get the alternator charging and it should hold until you turn the engine off. With a momentary switch you won't forget to turn it off and fry the alternator. Once charging the alternator does not need the external voltage as it supplies it's operating voltage internally.

Also, the magneto switch opens for run and closes for kill
Distributor switch closes for run and opens for kill
 
10 gauge on the charge wire from the alternator or it will smoke on you. On machines with a mag I install and oil pressure switch to turn on the excite circuit that way you do not need to install any thing special in the wiring. Simple oil pressure switch turns on at X number of PSI and that way no problems figuring out how to kill the engine and yet turn off the excite circuit. I used the oil pressure switched like what was used on the Chev Vega which turned on at 15PSI
 
So far I'm a fan of the "Denso mini alternator" you can get on ebay for around $60 shipped. I used it in my Super A. Its 1 wire and excites just off the lowest idle. Its on its first season so I can't speak to the longevity yet.

I will ask if you have a magneto ignition and no lights....then why bother with a battery and alternator? :shock: I can see if lights are in the future or if someday you are planning to go to a distributor ignition.

If the upgrades are planned then I'd wire #10 awg. I fused between the alt and battery with a weatherpacked 30A fuse holder, also found on ebay, I believe its some sort of a marine part actually. Keep the water out of the wiring and live a trouble free life :)
 
where could I put a key operated switch?
Could I replace the toggle that i have with
a key so I can take it with me once I turn
the tractor off and would it prevent it
from starting?
 
I'm thinking a wire from the mag pull switch to the one side off an on off key switch then another wire leaving the other side off the key switch going to the mag. Basically I'm adding a key switch to the middle of the run from original pull switch to mag simply breaking the connection...yes no ??
 
(quoted from post at 12:58:06 07/21/17) I'm thinking a wire from the mag pull switch to the one side off an on off key switch then another wire leaving the other side off the key switch going to the mag. Basically I'm adding a key switch to the middle of the run from original pull switch to mag simply breaking the connection...yes no ??

You kill the fire by grounding the mag and you make the alternator charge by sending voltage to excite it, to the Field terminal. So you only want it to provide ground to the mag when you are not providing 12v to the alternator. One way to do this and use 1 Single Pole Single Throw switch, would be to pair it with a relay. The switch will provide 12v to the alternator , but the switch will also trigger the 12v relay that will open when turned on. You would wire the mag through terminal 30 and out terminal 87a which should be NC and connected to ground. It will provide the ground to kill the engine when the switch is off in this way.
 
Will not work. A mag is grounded to kill the engine and an alternator has ti have voltage going to it to excite it. That is why I say use a simple oil pressure switch and leave the rest of the wiring alone. That way you keep it simple You know the saying KISS
 
I hope you are not referring to me, saying that adding a relay wouldn't work. If he already has a switch going to the alternator he could add the relay in much easier than he could plumb in and then wire the oil pressure switch. Plus the relay would be less than $5 and a very simple solution.
 
Old, how do i add a key then? I need something tho prevent someone from easily walking up and just starting the tractor...
 
Basically fellas I would like to know how to add a key so I can kill power inn the case someone wanted to steal the tractor it would be tougher than just starting it up or prevent a kid from potentially starting it by playing with it because basically right now anyone could walk up a and start it, unlikely but I'd rather have a piece of mind that my son won't inadvertaly start it and get hurt
 
A simple key switch will not work because they are open circuit when off and closed when on. About the only way to keep it from being started easy is to add a battery disconnect. Never found a key switch that has a closed circuit when off
 
A simple key switch will work if you wire the relay in to the mag ground wire and trigger it with the key switch as I said above.
 
Problem is with a relay to work as needed it would draw power when ever the ignition switch was off so it would slowly drain the battery. Never yet found a key type switch that was set up to work on a mag system
 
hate to disagree with Old below but some lawn mower key switches have a grounding terminal for the magneto and power terminals to turn on lights, magnetic clutches ect. in the run position and activate a starter relay in the start position however I believe most of these use the same key but should stop kids from accidently starting tractor. hope this helps as more info to advice below. Leroy
 
(quoted from post at 15:10:08 07/21/17) Problem is with a relay to work as needed it would draw power when ever the ignition switch was off so it would slowly drain the battery. Never yet found a key type switch that was set up to work on a mag system

You hook it to the NC lead of the Relay, it will not draw power when it is off. It would not drain the battery. Look at some diagrams for a relay, they have a terminal 87 and 87a , the latter is NC and the former is NO.
 

And in case anyone isn't aware NO is Normally Open , meaning the switch is open when the coil is energized, and NC is Normally Closed, meaning the switch is closed when the coil is not energized (i.e. provide ground through it to the mag when the key is off)
 
(quoted from post at 15:56:51 07/21/17)
And in case anyone isn't aware NO is Normally Open , meaning the switch is open when the coil is NOT energized, and NC is Normally Closed, meaning the switch is closed when the coil is not energized (i.e. provide ground through it to the mag when the key is off)

EDITED to correct. I missed the not when going back and changing some wording.
 
30AMP_Relay_8192.JPG


Look at the path from terminal 30 to terminal 87A, this provides closed switch when there is no power to the relay and this is what I was suggesting be used to ground the mag when the key was off if he wanted to use one key switch to control both the mag and the alternator.
 
Ya while mags are good in some cases they cause other problems when one to make them so some one cannot start them up when you do not want them to do so
 
Yes some of those do but the way there made it would be very hard to rig up a way to mount them but yes I forgot about those key switches
 
I searched far and wide for a magneto key switch. I finally found one at an old car electrical supply place called AutoReWire.com. I went to their web site today and couldn't find it the switch, but may be able to call as their on line catalog doesn't seem to be working. The switch was Item # 301350111564 and was called "Magneto Ignition Switch Tractor Allis Chalmers Advance Rumely Caterpillar". I bought it about one and a half years ago. It works great.
 
Thank you so much fellas, I'll look up that magneto key but I think the best way would be to use a keyed battery disconnect. Thank you all for the insight, I'm gong to look into everyone's solutions once I get back out to the tractor
 
You might try an boat shop since all the original outboards had mag terminals and also had battery terminals to power the starter, lights and other items. They might not be real cheap but it might be worth a try. Even a lot of the lawn tractors had the same type of contacts on the switch.
 

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