I was going through some of the stuff I have stored on my computer over the years and ran across this guide to converting to an alternator.I ofter see questions on this subject here and thought that this might help to answer some questions.Takes a while to digest all of the info but it's worth the read.............Moose With proper consideration to each of only some few matters the 6-volt generator to 12-volt alternator conversion is easily and well done by any sincere shade-tree mechanic. This guide provides information on alternators, voltage regulators, ignition coils, belts and pulleys, mounting brackets, dash gauges and other accessories and devices.
The Delco 10SI alternator is the top choice for a 12-volt alternator conversion. An alternator conversion is attractive because it offers more power, less maintenance including the option of using low-maintenance sealed batteries, and increased reliability. The SI series alternator made the 12V alternator conversion more reliable and popular because it introduced an integral, solid-state voltage regulator which eliminated the troublesome OEM external electromechanical voltage regulator. The 10SI is the choice of the SI series because the 10SI starts charging at a lower engine RPM and because it produces more amps in the lower RPM range than the other SI alternators. You can see the lower RPM performance on this 10SI curve. This low RPM performance remains important in industrial and agricultural power units and continues to be relevant to the early model, lower RPM engines. The 10SI is the top choice because of its price, availability, performance, reliability and suitability. 10SI physical dimensions.
Perhaps there are early model fire trucks, ambulances or other special equipment vehicles which require more than the 63-amps produced by a 10SI but generally the 10SI has enough capacity for vehicles up to and including later model, air conditioned family sedans. You can use your ammeter to measure amps by switching on each device in turn while the engine is not running or turn everything on to read the total amp draw. You need some margin of excess capacity and 42-amp total draw leaves a very comfortable 50% margin of 21-amps for the 63-amp alternator. You can lower the amps required by the lights and devices now on your 6-volt vehicle.
Replacing 6V devices with 12V devices will cut the amp draw by half meaning you will have more alternator capacity available for additional devices or to provide the margin of excess capacity. When converting to 12-volt from 6-volt one can typically and easily replace light bulbs, flashers, wiper and blower motors and other voltage sensitive devices with 12-volt equivalents and the replacements use 1/2 of amps.
The 12AWG wire used with many generators is just large enough for the higher maximum amp alternator; just barely and only if the wiring is not exposed to very high operating temperatures and the alternator is not heavily loaded. Of course your system may never draw, and that wire may never have to conduct, the full 63-amps so many run with the 12AWG and accept the risk the wire and alternator might prematurely fail. It would be unwise to not replace a 14AWG or smaller wire. Replace with at least a 10AWG wire. Here is a wire gauge selection table. Under-sized wire unnecessarily loads an alternator, or any electrical device. If a wire feeding a motor is too small the wire will be over-loaded, the motor will be volt-starved and you can expect the wire and the motor to prematurely fail. It works kind of the same way except backwards for an alternator which is additionally loaded and harshly over-worked by a too small wire. I'm talking about all the wire between the alternator charging post and the battery which usually means a termination on the starter solenoid because there's a cable from the battery to the solenoid and that cable is big enough.
Voltage regulator & wiring the alternator:
The internally regulated 10SI 12-volt alternator conversion does not need and cannot use an external voltage regulator (VR) or cut-out relay so you must disable, jump around, modify or remove what you got. Up to you if you want to remove what you got and rewire the harness, jump around what you got and use it as nothing more than a terminal block, or get inside what you got and make jumps and modifications so outward appearances remain the same. Here's what you need to know: one, the large wire on the generator (only wire on some generators) is the charging wire and it runs to the VR or a cut-out relay. A vehicle will not have both a VR and a cut-out relay. The other side of the cut-out relay or another terminal on the VR will run over to connect to one side of the ignition switch (other side of switch goes to the ignition coil), one side of the ammeter (other side of ammeter goes to the battery via the solenoid), and one side of the light switch (other side of switch goes to the lights). The wire from the VR or cut-out relay typically comes together with the wires off the ignition switch, ammeter, and light switch on a terminal block. So one, the charging wire that runs from the generator has to be tied to the other side of the cut-out relay or that other terminal on the VR; so much for the charging wire. What remains is that the remaining wire coming off the 10SI alternator connects to the other side (ignition coil side) of the ignition switch which can happen by connecting to the other side of the terminal block or even the hot (ignition switch) side of the ignition coil. Any remaining wires on the generator or VR are not used and should be removed or dead-headed. So that gets the engine running and the battery charging but now the OEM 2-position ignition switch won't shut off the engine. A multi-position Off/Start/Acc/Run ignition switch will shut off the engine because you connect the alternator to the ACC terminal. So now you need a trick to shut off the engine.
The trick is to put a one-way block in the wire between the alternator and the ignition coil side of the ignition switch. I recommend a diode but a light or some other resistor will do well enough if the vehicle is operated often. The diode block prevents any battery discharge while a resistor dramatically slows down any battery discharge. That diode block or resistor allows you to retain and use the OEM 2-position ignition switch. The diode block is not required when you have a later-model, multi-position ignition switch.
There are two diagrams that may help. Here is the fundamental charging and ignition circuit. Cut through the clutter of unrelated wires, doodads and gizmos and your vehicle is pretty much the exact same thing. Here is the straight up 10SI connection diagram.
Reversing the polarity:
An alternator most always requires a negative ground so you may have to do a few things. You must re-install the battery with the negative post grounded. You must change the wires from one post of the ammeter to the other and vice verse or the ammeter will read backwards; e.g., discharge while charging, if you don't. Ford loop-type ammeters can be reversed by pulling the wire out one side of the loop and threading it back through from the opposite side. The test is to see that the ammeter shows a discharge while cranking the engine with the ignition switch turned on. On a running engine you turn on the lights and the needle should move in the discharge direction. It's a good thing to reverse the primary (smaller, low voltage) wires on the ignition coil by moving all the wires on the coil's positive (+) terminal to the coil's negative (-) terminal and vice verse. The ignition coil wire swap is not that big a deal so don't fret if you can't get it done. You may continue to use a stock 6-volt ignition coil if you install a voltage drop resistance. Here is the ignition coil voltage drop wiring diagram.
Most any usual automotive starter and electrical accessory can operate as either negative or positive ground with no change in performance or direction. A 6V starter will last a good long time especially if you let it cool-down one-minute for every 15-seconds of cranking. A 6-volt starter solenoid may also last a long time but replace it with a 12-volt when the time comes.
Six-volt accessories and devices like gas and panel gauges and radios need special attention. Those devices are not simply on/off because they draw a varying amount of amps during normal operation. Compare to an ignition coil or wiper motor that is either on or off and the amps do not vary during operation. You will get fine results with a simple, but properly sized, resistor voltage drop (constant resistance matched to a constant demand) on an ignition coil or wiper motor (note that a single, same-size resistor does not fit all and any motors or other device) but you will not typically get fine results using a simple resistor voltage drop. On those other devices the amps vary. A gas gauge has a difference resistance and different amps at empty then it does at full. A radio uses less power at low volume then it does at full volume. You need to use a constant voltage/varying demand voltage drop and that will be some type of electronic device.
One-wire 10SI:
The Delco SI 1-wire has its uses. It is used on agricultural irrigation engines and in marine applications. It has been used on automobiles and other vehicles because it's easy to install and does not require a pigtail connector. That's not to say the 3-wire is difficult to install. The pigtail connector is available and will give access to the superior regulation provided by the alternator's solid-state voltage regulator. The one-wire cannot "sense" and adjust its output to provide a constant vehicle operating voltage depending on the load demand. The one-wire is a good fit for an irrigation engine that runs at one speed, has a constant load, and constant demand. An external relay must be used with a 1-wire to operate an idiot light in the dash. One-wire alternators also have "turn-on" issues because it must self-excite using residual magnetism in the iron parts of the alternator. If there is magnetism in the parts and the alternator is run up fast enough then enough power is produced to excite the alternator and it will ramp up the output. If it sits so long that no magnetism remains then that does not happen. The one-wire sitting idle will drain a battery over time. The 1-wire is not the better choice for engines that may sit idle for long periods, may be operated only at lower engine RPM's, use a dash light, engine RPM routinely varies, or where blower motors, headlights and other load demands come and go. My Ford tractor idles at less than 400-rpm and normally operates just over 1500 so I would always have to be certain to rev up a self-excite, 1-wire alternator so it would begin to output regardless of how I will otherwise operate the tractor. I don't mean to take anything away from the one-wire alternator but the standard three-wire is a more sensible alternator for most any application. One-wire alternators are also more expensive and not as readily available.
The 3-wire will always turn-on at the lowest possible RPM because it is excited by the battery voltage via the ignition switch to the alternator excite terminal right from the get-go. The 63-amp 10SI won't put out amps until 1,000+RPM but it is turned on and ready once the switch is on. The 3-wire with a diode in the excite wire will give you the lowest RPM turn-on possible and eliminate any battery-draining leakage current during long down times. The 3-wire hook-up is straight forward with one wire going no farther than the alternator itself. The 10SI alternator wire harness with the DA-plug makes it a snap to wire up the alternator. The harness also makes it simple to keep the dash light in the circuit. No additional resistor is required when using the diode. The 63-amp 10SI begins charging at a lower RPM than any other size (amperage) 10SI, even the lower amp 10SI's. Big plus when using the diode is that it allows you to continue using an OEM on/off key-switch. You can use the standard 10SI pig tail if you have an off/on/start/run ignition switch so you can isolate the alternator from the battery by connecting the alternator to the accessory terminal.
Belts, pulleys, and brackets:
Modern belts do not fit older vehicles so the pulley that comes with a standard 10SI will not match many early model vehicles and engines. Vintage autos likely have at least a 1/2" wide crank and water pump pulleys and agricultural or industrial engines may have 5/8" or larger pulleys. To get the 12-volt conversion right means you need to measure the pulley on the crank or water pump and install the proper wide-belt pulley on the alternator. My pulleys are small diameter so to get that alternator up to speed at lower engine RPM. Don't measure the existing v-belt because no telling how that type and size belt came to be on your engine; measure the pulley. There is a lot to v-belts and running the improper belt can be no end to problems and premature failure. You also pay for a belt/pulley mismatch in horsepower (mileage). You can find most vehicles' belt size on this parts interface look-up. Note: after completing the type, make, model, year selection, keep clicking on the part number until you get a pop-up Product Detail which shows Top Width (In.).
Clocking the alternator: Keep the regulator connector pigtail wire harness away from the manifold and in a location where you can get at it. The Delco 10SI alternator can be "clocked" to bring the wire harness pig tail receptacle around to whatever location so that engine parts do not interfere with the alternator wire harness. Two things to keep in mind when clocking the 10SI: one, the laminated ring between the front and back case halves goes with the back case and not with the front (drive-end) case. Two, you have only a long 1/16" difference between the brushes slipping out of the brush holders and not slipping out of the brush holders and you do not want the brushes to slip out of the brush holders. With that in mind, remove the 4 long case bolts. Ease the case apart a total of 17/32" (you begin with 7/32" space so the total movement will be another 5/16") and then rotate the drive-end case. You'll know the brushes slipped out of the brush-holders when you hear a rapid click-click or when the case won't go back together with only gentle to moderate pressure. If the brushes slip out then pull the case completely apart and reset the brushes as follows.
There are holes in the brush-holder for a drill bit or piece of wire that can retain the brushes and springs while you reassemble the case. The holder must be long enough to stick out the hole in the back of the alternator case. Other than wanting room for more fingers, it's no big deal; 2-minutes on a good day, 20-minutes on a bad day. Just remember, easy does it and if you have to push anything with more than gentle to moderate pressure then it's not right and you need to back up to see what you got wrong; that includes springs, brushes, wire, and case halves.
Note: the laminated ring between the case halves goes with the back case half and not with the front pulley end case half.
Dash gauges and instruments:
You have dash gauges or you have an instrument cluster. Older temperature and pressure gauges will not be electrical gauges. Some electrical dash gauges run right off 6-volts (very early models and then mostly GM) while other dash gauges and nearly all instrument clusters use 5-volts. The 5-volts is done by an electro-mechanical instrument voltage regulator (IVR) fed hot with 6-volts. The IVR is often a 1" X 2" sardine-can-with-wires kind of thing that is going to be separate from the dash gauge but will be attached to the back of an instrument cluster. It may be built in to some instrument clusters (AMC/Jeep). A Jeep cluster might use an IVR that is a big wire/tube-looking thing between the 6V gauge and the 5V gauge both used in the same cluster. An IVR can be retained but the mechanical contacts and heater are a source of problems and change. Might be better to remove and wire around that IVR and use a solid-state 5-volt voltage regulator to update those gauges. Use a 12-volt to 6-volt voltage reducer to update gauges not associated with an IVR or to feed an IVR hot. Use a 12V to 6-volt regulator/reducer made to replace the IVR if you would like to remove that electro-mechanical IVR to upgrade your instrumentation.
Voltage reducing resistors are not the way to go with dash gauges and instrument clusters. Use a resistor and the needles will move but the gauges won't be telling you what you want to know. Put a little thought and effort into the voltage, use the correct parts and those old gauges can work very well and give you better information than they were able to provide the day your vehicle came off the production line.
