And this:::
ALTERNATOR CONNECTIONS
Some of this is obviously a repeat from my previous 12 volt conversion page. Click
"12 volt" on the navigation bar on the left side of this page if that is what you wanted:
There are four connections on the Delco 10SI, internally-regulated alternator. The connections are the large output terminal (BAT+), the ground terminal (GRD-), and two connections usually labeled 1 and 2. Terminal #1 is the "exciter" or "field" wire. Terminal #2 is the "remote voltage sensing wire".
No confusion regarding the BAT+ connection. This large insulated terminal is the one that provides all the current for your accessories and to charge the battery. On most Ford Tractors this terminal will be connected directly to the accessory post on the Ammeter Gauge with a #10 or even #8 AWG wire. The other side of the Ammeter Gauge should have only one #10 or #8 AWG wire that goes to the terminal where the battery cable is connected to the starter solenoid.
The GRD- connector is usually left bare, unless you will be mounting the alternator to your engine block with something other than steel or aluminum brackets.
Terminal #1
On most OEM installations is connected to a switched 12 volt accessory source through a dash mounted pilot light. This wire provides the "excitement" current to the alternator field windings. Leave this disconnected, and MAYBE your alternator will self excite, maybe not. Revving the engine might get it charging, but if you let it slow idle a bit, it may slip back into discharge (been there, done that). It's also probably not a good idea to regularly run a cold tractor engine at full speed just to get the alternator to start charging.
Some conversions connect the field wire directly to a switched accessory source, others recommend connecting to the ignition switch using a resistor, bulb, or diode. But that was not the way the Delco alternator was designed to work. The dash light is important. I will spare you the technical theory behind it and just say that there are properties inherent in a light bulb that cannot be duplicated by a resistor or diode.
Some folks replace the original two-wire ON-OFF key switch with a new OFF-ACC-IGN switch that has separate terminals for Battery, Ignition and Accessory. This allows you to power the Ignition and Field circuits from two separate terminals, preventing the alternator from backfeeding the ignition when the key is turned off, and allows the alternator dash light to work properly.
How The Dash Light Works
KeyOFF: No power to the ignition or alternator. If this wasn't switched off, it would run the battery down.
Key ON with Engine Stopped: The light "sees" a 12 volt drop across it, lighting it. One end is on ignition 12 volts, the other on the motionless alternator - same as if the alternator failed.
Key ON with Engine Running: With a good alternator both sides of the light now see 12 volts, so no current passes through the bulb, voltage across the bulb is 0, no glow. If there is a failure in the charging system the light will glow.
Dash Light Installation
Of course your 50+ year old tractor is not equipped with a dash light. But it's easy to add. A small side marker light bulb will work. Stick to the automotive type bulbs though. Many others will not be durable enough to survive the vibration they will get on your tractor. If you don't want to drill the dash you could put the light on a bracket near the key switch or under the hood. Mine already had an extra hole in the dash from a previous owner's start switch that bypassed the neutral interlock. I repaired the original start pushbutton and used the extra hole for my alternator light. Once you have a location for the light, simply run a #14 wire from Terminal #1 on the alternator to the light bulb, and from the other side of the bulb to a switched, 12 volt source.
You can also put a 10 ohm wire wound ceramic resistor (Radio Shack part No. 271-132) in parallel with the indicator light. This allows slightly more current to flow to the alternator field current at initial start-up. This makes sure the alternator will begin producing power at low RPM as soon as the engine starts. This resistor does not affect the functionality of the indicator light. However, it does get warm. Its basically a little 10-watt heater, so put it in a location where it won't melt anything. Added bonus: If the dash light fails this resistor will still allow field current to get to the alternator so it will continue to charge. You don't have to stop and replace the bulb in the middle of the day or worry about your battery.
Terminal #2
This is the Remote Voltage Sensing Wire and it should be connected to the main accessory terminal where your ignition switch, light switch, and other accessories get unswitched battery power.
The remote sensing wire is supposed to sense system voltage so the alternator can regulate the proper voltage to your ignition and accessories. Most people will tell you to just run a short jumper wire from Terminal #2 directly to the alternator output (BAT+ terminal). It may work OK that way, and it is certainly easier. However, if it would work correctly on every vehicle by wiring to BAT+ at the alternator, the Delco engineers would have wired it internally and saved the trouble and expense of a separate external connection.
Properly connecting the remote sensing wire, enables the alternator to regulate voltage to your accessories and more importantly to your ignition circuit. One difficulty with many 12 volt conversions is properly sizing the resistor to protect the coil. If the voltage sensing wire is jumpered at the alternator, it will lock down the alternator output and prevent it from compensating for other accessory loads. Actual accessory and ignition circuit voltage will be allowed to vary over a much wider range thta could cause hard-starting, no start, burnt coils, and other under and over-voltage related problems. The only way to guarantee maximum performance from your new alternator is to run a #14 wire from Terminal #2 and connect it as close as you can get to the main accessory terminal.
Finally - If I am going to all the trouble to do a 12 volt conversion I would also change the Ammeter to a Voltmeter. The 6 or 12 volt electrical system will work fine with the original Ammeter. Amps are Amps, this gauge does not care about voltage, so it will work ok. But it also adds two additional terminals that carry a LOT of current. Since a Voltmeter is not IN the circuit, very little current goes through it and it can be connected to any switched 12 volt source. A Voltmeter actually gives a BETTER indication of the condition of your battery and charging system. When you first turn the key on, you get an immediate reading of battery voltage. A reading of 10 volts or less is considered dead, anything over 12 volts is at least a 50% charge and 12.6 volts is considered fully charged. While the engine is running the voltage should read between 13.5 and 14.5 volts if your charging system is working properly.
Here is a voltage chart for a 12 volt battery.
Simply divide the values by 2 for a 6 volt system.
