Farmall Super A 12 V Charging System Warning Light

majikfish

Member
I have a '53 Super A converted to 12 volt. Recently I noticed the warning light was staying on, and then it flickered and went out. What is the purpose of the warning light? It doesn't light anymore. I am not getting charge from the alternator to the battery per my voltmeter. Does that mean the alternator is definitely bad, or could it be wiring between the alternator and the rest of the system? What steps would you take to check/test? It's a new battery that will hold a charge.
 
Easy tests (assumes it is a Delco 10SI alternator: Pull the plug (or spade terminals) out of the side of the alternator. (be sure to mark where they came out.) Use a test light and go from to ground to the wire that was attached to the number 1 terminal. Turn on the ignition. If the test light and the Charge light come on (kinda dim, but on) the supply side of the excitation circuit is OK. If it does not, that wire (which feeds the alt a tickle of exciting voltage is not functioning. it could be the wire or the indicator light that have failed.
If the two lights do come on, the alt may be in need of brushes, or a new regulator (they are cheap).
Another test is to jump from the battery positive to the alt #1 spade terminal (with the #2 terminal hooked up to the output post where it is supposed to be). Start it. If it now charges, the wire and light are again suspect. if no charge, the alt needs to be checked at a parts store or auto electric shop. If it does charge on the last test, be sure to disconnect the jumper, or it will run down the battery.
A third check is to see if there is pretty strong magnetism at the rear bearing of the alternator when it is running. A screw driver held near it should be pulled onto the end bearing. Good luck, Jim
 
The light bulb is in the excite circuit so bad bulb means no power to the excite circuit of the alternator so then since it is not getting power the alternator can not charge. One simple way to check to see if an alternator is getting excited is to touch a piece of metal to the center area of the alternator where there is a cap looking thing. If it sticks because it is magnetized it is excited. If it does not stick then it is not getting the power to excite it
 
I replaced the light bulb. The old bulb was burned out. The light is now lighting up, but it stays lit the entire time the tractor is running. Is that normal, or does it indicate a further problem?
 
I replaced the light bulb. The old bulb was burned out. The light is now lighting up, but it stays lit the entire time the tractor is running. Is that normal, or does it indicate a further problem?
 
If it is a Delco 10SI, it is not correct. The exciting voltage from the ignition goes through the indicator lamp, then to the #1 terminal on the alternator. This connects to the voltage regulator module inside the Alternator. The regulator sends this voltage through internal switching circuits, to the field so the alt will start charging. As soon as the alt creates enough voltage, the #1 terminal is given system voltage. So instead of having a path to ground in the alt, the indicator light is given system voltage on both leads to it and it stays out. If the brushes in the alternator are worn out, it will light the indicator. If the Voltage regulator is bad it will light the indicator, If the wire to the #1 terminal is shorted to ground it will light the indicator.
Pull the #1 spade connector off of the alt and turn on the key. if the lamp lights the wire is shorted to ground between the indicator and the ALt. If it goes out, Have the alt checked at an Auto Electric or parts store. Jim
 
Light bulb that stay lite most of the time says a bad alternator but I have seen more the none that would still be charging and the light bulb would dim some but still stay lite. That is why they are called idiot lights and a gauge tells you what is really going on. Time to check battery volt when it is not running then check when running. Not running you should have around 12.5 volts across the battery and running you should have 13.5 to 15 volts.
My self I always use a diode when wiring up an alternator
 
You have a voltmeter on the tractor. What does it say?

If it is not up around 14V, then the alternator is not charging.

Just like on a car, the "idiot light" should go out when the alternator is working.

Have you tried revving the engine up to full throttle to get the generator to start charging? Sometimes that is necessary because the engine isn't turning fast enough at idle to make the generator charge at first. Once it's charging at high RPM, it will usually charge at idle.
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top