farmall super a battery

05-31-2011 06:08:54
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My Super A uses a 12v battery setup for postive ground. My son decide to use it to jump off another tractor and fried my battery. After replacing the battery I notice the alternator smelled burnt and its not charging. Any suggestions. My alternator has one wire hook to it with diode in series, what exactly is the diode for. Also has what looks like a ground wire also on the alternator. Any suggestions would appreciated. Not too familiar with this type stuff.

Your son (or you) also fried the alternator. If there is one thing an alternator cannot stand it is reverse battery connections. Diodes in the inside (big ones) convert AC to charging DC. This setup allows current to flow in the direction of charging only. A battery hooked up backwards causes the diodes to appear as short circuits to ground. This pops the internal silicon parts of the diode. Rebuilding the Alternator (probably a diode pack, and new regulator is needed)
You state that it is positive ground!! Almost al alternators are negative ground. Farmalls were positive ground from the factory with a 6 volt generator, but when it was converted to an alternator it was probably Negative ground. If there was confusion in this regard, bad things do happen. There are positive ground alternators, but special ordered, or for particular vehicles. Not common.
The Delco 10SI alternator has a external diode (probably OK) that allows ignition voltage to excite the alternator starting the charging process. The diode prevents electricity from reversing in that circuit keeping the engine running when the key is off. The third wire should go from Terminal #2 on the alt to the big post, (short wire). If the diode in the ignition wire mentioned has its index white band toward the alternator, it was a Negative ground battery/charging system. Jim
Best of luck, and always go from pos to pos and neg to neg no matter what the ground is when jumping.

Better tell son to check the posts before hooking up to jump anything hes luck it didnt blow the battery.

Went and checked out the alternator and battery last night. The battery is set up for a positive ground. I have a ballast resistor right before the coil to drop the voltage. On the alternator I have an external diode on the cable going to the #1 terminal and back to the switch.On the post lug I have a bigger red wire going back to the battery or the starter,didn't get to trace it back for sure though. This was set up like this since I have had the super a. The ammeter showed it was charging. Any ideas what I have? And how to get it charging again. Do I have a negative ground or pos ground alternator?

The least expense, and best approach would be to make the following changes. With the battery not connected.
1}Remove the alternator and replace it with a 10SI rebuild negative ground from the parts store of your choice. (Not a one wire setup, but a standard 10SI.)
2}Change the wires on the amp meter from one side to the other.
3}Make sure the diode in the #1 Alt lead is placed such that the index band (marking on the diode) is toward the alternator, and the other end attaches to ignition source. Check the diode to assure it is passing current one way and not the other. (Ohm meter near zero one direction, and near infinity the other.)
4}attach a short wire from the #2 terminal to the out put stud of the Alt. (senses system voltage)
5}Switch the coil so that the Negative small terminal is attached to the distributor lead, and the Positive is attached to the ignition ballast resistor.
6}Reinstall the battery with negative ground.
Run the tractor!

Jim

Thanks for the input. I will be changing it 12 volt negative ground soon. Thanks again