Farmall Cub

with all of your help i have found a wire diagram by rudi.i have a couple of questions with hopes to find answers.in this dia.it shows a wire comming from the starter to the amp meter (is this the + side or the - side ?)then to the battery terminal of the alternator with 10 guage wire. i am using a delco cs121 105 amp alternator which i was told could burn up the 20 amp guage that is original to the cub.would i have to use a volt guage in its place and would that change the whole wiring dia. also where would the hot side of the ignition switch come from ? i'm hoping rudi or someone can help.thank you,john

Boss Hog is the best 12 volt conversion man. He'd be the one to ask! Ed

105 amp alternator is way over kill for the Cub. I would pick up a single wire Delco clone in the 60 amp range. Even a 60 amp alternator is more than sufficient.

Simpler to change out the amp gauge to one matching your alternator's output.

Wiring up the amp gauge. Worst thing that can happen is you have to switch the wiring on the back of the gauge.

Hot side of ignition switch. Most convenient place is on the amp gauge, negative side if you want to see the needle move when you turn on the ignition. If you use the 105 amp alternator and a matching amp gauge you may not even see the gauge needle move when you turn on the ignition. In this instance just wire the ignition to either terminal on the back of the amp gauge.

Just looked up the Delco CS121 alternator. It's a true one wire alternator. But the retail price on several internet sites is $240-.

The 60 amp Delco single wire clone is in the $50- range at most auto parts stores.

I am no electrical guru. I am just the manual guy ..... However, we do have some great resources..

This is one of Bob Melville's excellent schematics and this is for a conversion from 6v to 12v alternator.



I do know that you will have to size the ammeter to the load from the alternator. And yeah, I agree with Eugene a 105 amp alternator is really overkill. Either the GM 10SI or the Hitachi will work nicely.

I used a CS120 on Cubota, because I had it laying on the shelf. It is overkill for sure! I did convert to a volt meter and yes, it wires differently. The shunt in the 20 amp meter doesn't stand a chance with the 105 amp alternator. If you decide to stay with the amp gauge, get the highest amp rating you can and upsize the wires, starter to amp meter and amp meter to alternator, to at least 10ga. wire. You're going to find that the high output will have a negative effect on idle quality. The compact size of that alternator is nice, however.

good morning guys,its raining here again so stuck in the houst for awhile.spoke to boss hog yesterday and he gave me a wealth of info.so i did a little more recerch.come to find that i was misled and misled you all.talked to a friend in azorinathat has been remanufacturing alternators and starters for many years.he told me that this cs121 is a 61 amp alt. looked for the #s stamped in the body and sure enough stamped clearly 61a.also has a diotrio in it so i don't have to worry about feed back when turning the engine off. i will have to use a 12 volt amp meter and he did tell me how to wire it. i will let ya know how it goes. gary dorson brought up negitive effect on engine idle quality with high output alts.can you explain that a little clearer. eugene,i was lucky for once,i got three of these remanufactored alt.for much much less then the retail price yuo mentioned.thank you for that uplift.you all have a great day and thanks again for being so informational,john

jiw01 wrote:i will have to use a 12 volt amp meter and he did tell me how to wire it.

You just need an amp gauge capable of indicating 62 amps or more. Voltage is not a consideration.

gary dotson brought up negative effect on engine idle quality with high output alts. Can you explain that a little clearer.

It takes energy from the engine to power alternators, generators, fans, etc.. Doing a bit of rough math it would take about 1.9 HP from the engine to power a 102 amp alternator, 14 volts, at full draw on the alternator. A guess, that's about 1/3 of the engine's hp at low idle.

I have a 62 amp Delco single wire alternator on my Cub. The amp gauge swings to charge upon engine start up. Usually, by the time the engine comes off choke during initial start up, checking oil pressure, climb into seat, the amp gauge needle is showing a very low charge rate. The Cub engine handles the 62 amp alternator without a problem.

now that i have the hood and fuel tank off,is there any info or pictures on how to rig some type of temperary fuel tank so that i can test run the system? thanks again

John:

The answer would be yes:

How To Mount A Pony Tank
How To Make A Temporary or Pony Gas Tank

These are two that we have in the CBoK - something that is worth perusing. There are many other ways to do it as well.

I use an outboard motor gas tank set on the tractor seat. The type of tank with the priming bulb in the fuel line.

rudi,eugene,thanks to both of you.both great ideas,i will see what i can come up with.have a great day

Rudi wrote:I am just the manual guy .....

This is one of Bob Melville's excellent schematics and this is for a conversion from 6v to 12v alternator.

You're more than that, Rudi! Is there a specific part number I should be looking for for the warning light?

Posco wrote:You're more than that, Rudi! Is there a specific part number I should be looking for for the warning light?

The part numbers are located in the lower left corner of the wiring diagram.

Easier to install a diode in place of the light bulb. I'll see if I can find the diode part number.

Edit: https://www.google.com/search?q=bob+mel ... B661%3B516

Diode part number, lower left corner.

Nother edit:

artc wrote:you can install a diode (1N4004 or equivalent) in the exciter lead to drop the voltage to the #1 terminal by .7 volts. it still needs to be switched off the ignition, but that will tell the alternator to charge. try that first.

I found this to be interesting. Not directly related to this topic but these guys sell conversion kits to make a 10Si alternator work with a 6V pos. ground system. http://alternatorparts.com/10si-all-in-one.html#ckits It may be of use to someone.