6v Magneto Ignition Wiring ?

Apologies in advance for the long winded post, but from what I’ve read of these types of topics here, the more information the better.

I have a 43 CASE VAI, 6V with Magneto Ignition, no lights or multi-position light switch, only the on/off pull knob switch. There is currently an old corroded, what appears to be 2pole VR mounted on the generator. I am by no means an electrical expert, but I have read and re-read all the threads I could find for wiring diagrams and checked and doubled-checked my wiring and all appears to be wired ok, I think, but I not seen a wiring diagram for my setup with lights or light switch.

The Ammeter never budged at all when turning the ignition on/off or running the tractor regardless of engine speed so I suspected a frozen needle inside it from decades of sitting outside. I replaced it and have it wired as shown below. With test meter, neg to neg battery terminal, I get 6.2 volts on either post of ammeter when touching positive lead of test meter to those posts, from what I’ve read that’s should be correct BTW, does it matter what terminal (left or right) this Bat wire from the VR is connected to on the ammeter, as long as it’s not the same terminal that is also connected to the Battery via the starter switch.

Since I don’t have any lights, I’m thinking I really don’t have any significant load anyhow while the tractor is running. Isn’t a magneto ignition self-supporting sort of speak? Meaning the only purpose my generator and VR are serving is to recharge the battery after using the starter. When I push the on switch in , according to the manual, that’s correct for a magneto ignition, In = On, the ammeter needle barely moves, if at all. Tractor will not run with on switch knob in the out position. I have properly polarized the generator by momentarily touching a jumper wire from the A terminal on the VR to the Bat terminal and did get a little spark when doing so, but only once. After disconnecting the battery and reconnecting a 2nd time and trying to repolarize, did not get any spark. Since I don’t have lights, I can’t turn any lights on to see of the ammeter needle moves to the discharge side.

So, when I measure voltage across the battery terminals with the tractor off or running at idle , I get about 6.19 to 6.23 volts on digital test meter, no change in movement of ammeter needle. At higher RPM’s, voltage across Battery terminals varies between 6.26 to brief peaks of 6.3+, maybe 6.4 for a split second. Needle in new ammeter is wild at higher RPMs, bouncing feverishly between 0 and 6~8 amps. Bouncing so much it bounces back into discharge side of the gauge, -2 or so.

So I’m suspecting the old corroded VR. I suppose it could be the Generator, but working my way through the least expensive items first. I received a new VR but have not connected it yet because the old VR only has 3 terminals; F, A, & Bat and the new one has F, A, Bat, & Load. Since I don’t have lights or a light switch, I have nothing to connect the Load terminal to. Can I just ignore this “L” terminal on the new VR and go ahead with the other connections or should I exchange it?

If the new VR doesn’t work, I’ll bring the generator to a generator rebuilding shop and have them check it out.

Hoping if I can get this sorted out here, this thread may be beneficial to others in the future with a similar set up.

Thanks

The magneto is a stand alone system. It should have no connection to battery voltage source. Generator should have no effect on magneto

With no distributor and no lights there is no significant load to cause ammeter discharge indication. Starter current does not go through the ammeter. Your generator will only recharge the battery to replace starter draw.

The magneto on-off switch opens to allow the system to operate and grounds the magneto to kill spark and shut down the engine.

L on the new regulator is for "Load" that is distributor ignition switch and light swirch source. You will leave yours unconnected

On your diagram, the wire from ammeter to starter switch should go to battery side, not starter side of the switch.

1) A good properly charged 6 volt battery should measure around 6.3 volts setting there with the engine not running, but if the engine is running and the charging system works the battery voltage should rise to at least 6.5 up to near 7 volts at fast RPM. If not the charging system isn't working......... SEE MY CHARGING TROUBLESHOOTING PROCEDURE LINKED BELOW:

2) The ammeter is a pass through 2 terminal In/Out series device which has its LOAD terminal wired to the BAT terminal on the Voltage Regulator and its SUPPLY terminal wired to the hot ungrounded battery post often via a wire from it to where the big battery cable attaches to a starter switch I.E. that's the voltage SUPPLY.

3) The ammeters SUPPLY terminal has but one wire, that's the one to the battery often wired to the big battery cable on the starter switch, while its LOAD terminal wires to BAT on the VR PLUS feeds voltage to loads like Lights and Ignition etc. UNLESS you have a VR that has the (L)OAD terminal in which case its where lights and load get their supply input voltage. IE wire LOADS (input to light switch) to the VR's L terminal if it has one.

4) If the ammeter is wired right and working if you turn on lights engine not running it should swing over to - discharge and when running if the genny works swing over to + charge. If it does the opposite swap its leads. A Mag being ON (NOT grounded) or OFF (grounded) has no affect on the ammeter while a battery powered coil ignition does.

5) A Magneto is not dependant upon or have anything to do with the battery or charging system. It uses a KILL SWTICH which when connected to frame ground kills the spark. Such an ON/Off switch is merely a 2 pole single throw two terminal switch wired between the Mag and frame ground. When ON its open when OFF its closed.


You have to FIRST get it wired right for that VR with the L terminal and then run my Troubleshooting Procedure to see the cause of no charging.

John T
John Ts Charging Troubleshooting

Thanks guys for the tips and info, I finally had a good chunk of time this past weekend to dig into it.

Worked my way through the wiring again, all good, except moved the wire from the ammeter to the neg supply side of battery via starter button as suggested.

Then proceeded with your troubleshooting guide;
1. Check
2. Check
3. Check
4. Check, but ammeter still jumped around all over the place.
5, 6, 7. No change, bummer on to 8
8. Check & check, genny performed as described, now I was really baffled.

Opened up the metal band on the Genny, brushes looked o.k., each 3/8"~1/2" long each, spring holders appeared to move freely. Commutator looked a little dirty, but having never really looked closely at one before I had no real point of comparison.

So with all the above tests done, now what? Tried blowing the Genny out with air, not much of anything came out. Then I remembered I had a can of Alternator cleaning spray on the shelf, sprayed that on the brushes and commutator and spinning it by hand with my finger covered with a soft clean cotton cloth cleaned the commutator. Kept doing this until the cotton cloth came up almost clean.

Put it all back together and tried again, shazam, ammeter swung to + side and was steady, no bouncing, voltmeter registers 6.3-6.4 at idle, and 6.4-6.8 at higher rpms, success !!!

Thanks again,


I posted a corrected diagram below in case anyone needs it in the future.