Mighty Mo and Friends
One of the most frequently modifications that are done to a Willys Jeep is a 12-volt conversion. While a 12-volt generator is an option, most people opt for an alternator and by far the most common is the "One Wire". However, many times the application is considered unacceptable because the alternator doesn't begin to charge until the engine reaches about 3,000 rpm. While this may not be considered a problem in a high revving short stroke engine, on the L134 and L226 3,000 is about the upper limit of where these want to operate. This 'problem' will be addressed later in the page.
The one wire alternator has an internal regulator and thus only one wire is required to go to the vehicle electrical system. While other types are possible to use, by far the most common is a Delco model SI. These are found on early GM products and therefore are easily available at most salvage yards or auto parts stores. Be sure to get a model SI and not a CS. The CS is riveted together and considered to be 'disposable'. While the SI is bolted together and easily rebuilt by the average person.
The Delco alternator is designed to operate using more than one wire going to the vehicle electrical system. In fact there were originally at least 3 wires. One BAT, one field and one sensing. Actually the field wire goes to the "idiot light" and then to the 'RUN' position of the ignition switch. The sensing wire either goes to the 'BAT' side of the ignition switch or the 'RUN' side depending on the application. When the ignition is in the run position the sensing terminal is energized with battery voltage and the field terminal is energized with a current limited voltage through the lamp. When the alternator starts charging, the field voltage raises and the voltage differential across the lamp reduces and the lamp goes out. The charging voltage is 'sensed' through the sensing wire and the internal voltage regulator regulates the voltage to about 14 volts.
When used in the one wire configuration, the sensing wire is connected directly to the BAT terminal. The field terminal is not connected. If the engine is run at a high enough rpm the regulator will "leak" enough voltage to the field to energize it and the alternator starts. The trick is to get the regulator to "leak" at a lower rpm, and thereby "self energize". Replacing the regulator with one that "leaks" is covered in the next section.
Actually, adaptation is quite simple. Just change the regulator to a self energizing one, connect the sensing terminal of the regulator to the BAT terminal and you are done. The trick is finding a self energizing regulator. The one I use is manufactured by TRANSPRO and is catalog number D10SE12. D10-Delco model 10SI // SE-Self Energizing // 12-12 volt.
Because not everyone tears alternators apart, I thought I would guide you through the process with pictures.
All that is "required" is to run a heavy, at least 10 gauge wire from the BAT terminal to the positive (+) post of your battery. I would suggest you connect it through the AMP meter. Depending on the information you want, there are a couple of ways to wire the meter. The first, and preferred, is to measure the charge/discharge of the battery. The other is to measure alternator output. The alternator output also includes the current draw of the lights etc. of the vehicle. Alternator output is best measured by voltage not current. The charge/discharge method tells whether the battery is charging or discharging.
Below is a schematic showing the preferred wiring method.
OK, so you have installed an alternator, wired it correctly and the thing doesn't charge. Now what?
First, check to see if the regulator is 'leaking sufficently'. This is done by connecting a test light between the BAT terminal and the 'Field #1 Terminal'. This should start the alternator charging. Actually this is the way it was designed to work. If the alternator starts charging, the regulator wasn't leaking enough. Follow the conversion above. If it doesn't charge, then continue below. (Read and understand the procedure fully prior to starting)
If it is suspected the alternator isn't charging the battery, the best indicator is voltage. When the engine is running, the voltage should be aproximately 14.7 volts DC on a fully charged battery. If the voltage is less than 14.7 VDC and the battery is fully charged, we can diagnose the problem by "full fielding" the alternator.
CAUTION: Full fielding the alternator can result in high voltage. This can result in damage to the vehicle and or personal injury. At higher engine speeds voltage can be LETHAL!
Conversion kits and complete alternators are available from JC Whitney - (no recommendation intended)
Conversion kits - or enter "one wire alternator conversion kit" into the Google search box
Complete alternators - Your local automotive parts is also a good place to buy
5/8" x 2 1/4" (wide belt) pulley - The part numbers is 98-NAA5825, but enter NAA5825 into the part number search box
Below are the schematics for the "as designed" and One Wire conversion.
Other than the external wiring, nothing else is changed. To get the 'One Wire' to start charging at a lower RPM the regulator is changed, as described earlier on this page.
I hope this page has been helpful to you. If you have any questions please email me at firstname.lastname@example.org I will try to answer any questions you may have.
Visitors since August 29, 2001
Copyright Richard N. Meagley Sr.