SA 12V Conversion

I would like to do a 12V conversion on my 1949 SA. It has a magneto ignition system, and a 6V positive ground system for the starter and lights. I plan to use a 1-wire Denso Mini Alternator. I know that I will have to change the light bulbs to 12V, but I am not sure what other changes I will have to make. For example, do I have to switch the wires on the ammeter? Does anyone have a wiring diagram for this conversion? I am assuming the starter can handle 12V for the short period of energization, as my engine starts very easily...one pull of the hand crank when I use it. Any help you guys can offer will be most appreciated. Thanks.
 
I never recommend a 1 wire set up due to needing high RPM to self excite. I do 3 wire and on that being a mag a 3 wire is very simple. Add and oil pressure switch to turn on the excite circuit switch to - ground which you need to do be it a 1 wire or 3 wire. Switch the leads on the amp gauge and run the charge wire to the + battery cable hook up on the starter switch.
 
1) Since its a Magneto Ignition there's no changes needed on the Ignition.

2) YES the leads need swapped on the Ammeter or it would read bass ackwards. On a One Wire setup the big main alternator
output stud wires to the LOAD (NOT battery/starter SUPPLY side) side of the ammeter replacing a wire that used to go
to the BAT terminal on a Regulator or Cutout Relay. I use 10 Gauge for that.

3) YES as you already know, change lights to 12 volt.

4) YES the starter can work at 12 volts, there are chances the starter drive may have issues but if so you can deal with
that. If I convert from 6 to 12 I DO NOT use a big honkin super high CCA 12 volt battery but instead a mid sized
unit so as to save wear n tear and shock on the starter drive mechanism.

5) A One wire is a simple set up as compared to a three wire. HOWEVER on some (Delco mostly) One Wire conversions they may not self excite quite as easy and may require higher RPM before they do so. The Denso may do better however ???? Insure a good and tight belt is in place to help with any such issue. Im NOT trying to talk you into the Denso or Delco or one or three wire since such was NOT your question. That choice is yours alone not mine.

John T
 
I helped a neighbor convert a 56 IH 1/2 ton pickup to Delco 10SI alternator rebuild. We purchased the alt. from O'Riley's (not a one wire). After installation and before permanently wiring it, we started the engine (Never above idle) I could not figure out why the voltage went to 14.3 with nothing connected to the #1 terminal. That alt started charging as a one wire at idle. It also had very low draw when shut off. I wired it as a 3 wire any way. But it was happy without the circuit. Not all are created equal. Jim
 
Good chance you got one of those bad right out of the box alternators. Seen it many times and it does not matter where you buy them it happens way to often. Most of the time I have them checked before I even leave to parts store. In my case it is O'Reilly's since it is them or auto zone and auto zone is a joke
 
I've been happy with the Denso mini alt, I have done 3 tractors with them as a 1-wire (SA, Cub, SMTA). The SMTA does not charge at idle but the other two do, but it doesn't take a lot to get them working.

My conversion was a distributor-based system so slightly different, and I haven't hooked up any lights (I don't currently tractor at night), but its just a couple more wires.

I replaced all of the B+ and the woven/braided ground straps with new parts when doing the conversion, smaller 4ga cables worked well. I used an Interstate MT-35 battery which just barely fits (may not fit with original sheetmetal which I don't have).

If your tractor starts easily then the 12v applied to the 6v starter does not seem to do any harm.
 
I call them auto clone because there a clone of a good auto parts tore but just like a clone if it is not taught how to do what the original does there worthless
 

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