DC alternator conversion

[unstyled Bob]

I am converting a DC case to 12 volt. The whole system was shot when I got the tractor. Cost way more to build the generator again than to convert. Armature and fields are both shot. Have a S10 Delco 1 wire . The adjuster arm hits the fan on the alternator. Was wondering about just taking the fan off and running it without the fan. Would that overheat and ruin the alternator. Otherwise I will have to build a new adjuster arm.

 

[wilson ind]

unless you are farming 12 hours a day with it I do not think any harm., Do you have mag? Mine with mag only uses battery to start. Used for 10 years with no battery charging except occasionaly every 2 months.

 

[Christopher Mikesell]

Yes, the fan is necessary for extended periods of operation and/or full capacity charging. The bigger issue though is that you will have problems with your mag impulse if you convert to 12V. Nothing will break, but the starter will turn the mag too fast to trip the impulse. Thus, you will have poor spark (tractor may not start until you take your foot off of the starter button). This is why so many DCs and SCs have distributor conversions.

 

[unstyled Bob]

Yes it's a mag. Been starting it with 12 volts. No problems there. I need the lights to work so that's why I'm fixing the charging system.

 

[tractorguy2]

I don't think the 12v will spin it so fast the mag won't work. The neighbor had a farmall M. He converted it to 12v it also had an IH mag. it started just fine. I don't recall him ever having starting problems or mag problems.

Can you move the adjusting arm to the back side of the mount on the alt?

 

[todd hamilton]

I don't have this sc case anymore but ran into same challenge. I took a piece of stock from the top bolt on the alternator to the original generator adjusting arm to make a "scissor." This pushed the top of the alternator out instead of up and down to tighten the belt. It looked a little jaky but it worked. Ran it like that for ten years. If memory serves the bottom hole mounted almost perfect.
sc case with alternator

 

[Christopher Mikesell]

It's not that the mag won't work, just that the spark intensity will be lower than either cranking it slower (impulse will snap the mag) or cranking it faster (spark will naturally be stronger). This is a common problem with SCs and DCs. Putting 12V to the starter will spin the case mag above the speed that engages the impulse, but below idling speed.
Here's the equation for the typical old tractor,

(poor compression)
+(poor carburation)
+(stale fuel)
+(less than new mag with glazed points/weak condenser)
+(cranking at a non-ideal speed)
=(common SC and DC starting problem)

Just do a quick search of the archives to learn more.