12V on W4

[henry v11]

I have a W4 with a Mag ign. If I use Bob M wiring diagram for conv to 12V what do I do with the ign sw as mine is for grounding the mag. What type of alt is best to use. Thank you.

 

[Andy Motteberg]

If you are going to change to a distributor, you need a 2 prong switch. If you are just converting so you have more cranking power, you can still use the magneto on the 12V system.

 

[John T]

If youre keeping the mag, the ignition grounding kill switch can remain as is, it has nuttin to do with the battery or ignition etc. being 6 or 12 volts as its NOT connected to any of that.

If youre changing to a battery powered coil distributor ignition, you need a regular On/Off push or toggle type switch to feed voltage to the coil when ON.

The thing is many alternator conversions use the ignition voltage source (the Ignition switch to coils voltage when ON) to excite a 3 wire alternator such as the GM 10 SI but if you keep the mag then you have to use an alternate method to excite the alternator (unless you use a true one wire) if you go with the 3 wire GM 10 SI set up.

I recommend the GM 10 SI 3 wire due to its cheap n readily available

If I was keeping the mag, I would configure a 2 pole double throw (DPDT) dash toggle switch such that in OFF it grounds the mag and theres NO excitation voltage sent to the alternator, but when ON it sends hot voltage to the alternators lil side No 1 terminal via an in line series current limiting 10 ohm safety resistor and the mag is NOT grounded......Some use an oil pressure set up to excite the alternator in mag tractors but the DPDT toggle On/Off switch wired as desecribed is best in my opinion...


John T