12 volt alternator

this is a 2424 international tractor already 12 volt. the alternator would never charge. purchased a 63 amp 3 wire. new battery. I followed the schematics on hookup. light does not come on when keyed switch is turned to on. the alternator charges but the light never goes out when it is running. have a volt meter installed. my wiring is no 1 wire to light and then to ign. no 2 is attached to the alt post. S on starter solenoid wire hooked to solenoid terminal on ignition switch.. coil wire from ignition goes to R on starter solenoid then to plus side of coil. new starter swich my problem is the light is not working properly and worried it is not wired right. all help would be appreciated.



thanks.

denny martin

Using a volt meter, unplug the harness from the back of the alternator, turn the ignition on. You should get 12v on the wire to the #1 and #2 terminals.

If you don't get 12v at the #1 terminal, check the connections back to the indicator light on the dash. The other side of the indicator light should be fed 12v from the ignition switch.

To make that alternator work, the small 1/R alternator post requires initial excitation voltage, while the other small 2/F senses voltage such as on the big rear main output stud.

To excite it with a dash "idiot light" it must FIRST have voltage such as from the Ignition switch IGN terminal (when turned to On/Run) orrrrrrrrrr some folks use the hot coil input which gets voltage to the coil when the Ignition Switch is turned to On/Run.

IT WONT WORK UNLESS THE IDIOT LIGHT IS GOOD AND HAS HOT INPUT VOLTAGE (like when Ign switched On) THEN TO THE ALTERNATORS 1/R TERMINAL

If all is correct, the idiot light glows (indicates no charge) when tractor is turned on before its started because it gets a ground via the alternator. HOWEVER once started the 1/R is near the same voltage as on the lights input so the light goes off.

To prevent run on after tractor is shut down, you may or may not (depends on idiot light) have to add a small 5 amp diode in the circuit from light to 1/R on the alternator, but usually the idiot light in the circuit prevents any run on.

1/R needs hot excitation voltage when ign switch is on, and if an idiot light is used, it MUST have hot voltage on its input when ign switch is on and its output wires to 1/R on alternator. Or if you don't use the idiot light a wire from coils input (hot when ign is ON) to the alternators 1/R with an in line series 5 amp diode (to stop run on) will give the alternator its initial excitation voltage.

Got it???

John T

"coil wire from ignition goes to R on starter solenoid then to plus side of coil."

Ignition from switch originally went to a resistor, then to + side of coil. R on solenoid originally went to coil +/resistor junction , with no wire from switch. System used a 6 volt coil, or "12 volt, external resistor required coil" with resistor dropping 12 volt battery source to 6 volt coil during operation. During brief cranking to start the solenoid bypassed the resistor applying full voltage to the coil for hotter starting spark.

Some one may have replaced original coil/resistor with a direct "12 volt no external resistor coil". If so, switched ignition should go direct to coil +.

I went to check voltage this morning and the battery was drained. I believe virgil is correct in that the coil wire should not be hooked to the r terminal on the solenoid, think that connection is draining the battery. I did replace the coil years ago and believe it to be a 12 volt. once battery is charged I will try and start it to see what I have. thank you guys for your input it is really appreciated.

R terminal on solenoid is "dead" until solenoid is activated, then voltage is applied internally. This should not be the cause of battery drain. I would guess there is a connection problem on the 1 or 2 pin on alternator that is causing the problem. Other guys have covered that.

Might as well explain to him that the purpose of the "R" terminal is to take the ignition ballast resistor out of the circuit and give full battery voltage to the coil during cranking.

found the problem. advance auto parts gave me an externally regulated alternator, I asked for a 3 wire internally regulated alternator. every thing is working as it should. thanks to all of you guys for your help, it was greatly appreciated. learned a lot about automobile wiring this week.



denny martin

Remember this and you will have no problem with parts guys. You want an alternator that fits a 1980 Chev pick up no power any thing no AC and you will have a a Delco 10si every time