You'll find a bazillion of them in the salvage yards. All domestic Chrysler products used them from 1970 through at least the early '80s. I think they were used through the '89 model Fifth Avenue rear wheel drive. You can also buy a new regulator for around 15 bucks. If you have a farm and home type hardware store, they will usually have them too.
They were mounted to the passenger side of the firewall and have a triangular three-pin connector but there were only two wires in it. The wire in the center is blue. The one on the side is green.
My personal preference for your truck would be to disconnect the plug or unbolt the terminal block from the back of your alternator and wrap it up so it can be easily put back to stock in the future if desired. Find a similar connector in the salvage yard to hook the new wires to it. Of course, grab the connector for the regulator too. It is held on with a spring-metal band that you have to squeeze on the sides to release the locking tabs.
Ok, here's where it gets complicated. You have two small wires on the back of the alternator that were bolted on or plugged in, (depending on the year). You have two terminals on the regulator. Connect the two pairs together. For simplicity, use green and blue wires to extend them from the regulator to the alternator. Either wire can be connected to either terminal on the alternator as they are just going to the two ends of a coil of wire. Polarity doesn't matter. (I hope you understand I don't mean tie all four points together). Connect the blue wire from the regulator to one terminal of the alternator. Connect the green wire from the regulator to the other terminal on the alternator. There, the hard part is done!
Only two more connections are needed. The first is simply to bolt the regulator to a clean, paint-free surface on the body. That is the ground connection. Don't go scratching a lot of paint off. The threads of the bolt should cut into bare metal just fine. The last connection is to splice into the blue wire and tie it to a circuit that turns on when the ignition switch is turned to "run". For many years, Chrysler used dark blue wires under the hood for any circuit that turned on with the ignition switch. I don't know if they still do that. You might look at the "park" wire on the wiper motor. I can help figure out something to tap into if you can't find anything.
That's it. When the ignition switch is turned on, a small current, maximum of about three amps, runs from the blue wire, to the alternator, through the field coil, out the green wire, to the regulator, through its control circuitry to ground. The current through the field coil sets up a magnetic field. (Hence, the name "field" coil). When current flows through a wire, it sets up a magnetic field. When a wire is passed through a magnetic field, it induces a voltage which causes a current to want to flow. The secret to generating a voltage mechanically is you must have three things: a magnet, a wire, (a wire wound up into a coil is much more effective), and most importantly, movement between the two of them. The movement is why the field winding must be spinning. That's why it runs off the belt. The magnet is the field coil's electromagnetic field.
That blue wire serves two purposes for the regulator. It provides the power to run the circuitry in the unit itself, and it is where the regulator senses system voltage. The goal is to maintain alternator output between 13.75 and 14.75 volts regardless of how much current it is producing. Think of the regulator as a variable resistor between the green wire and ground. As the regulator senses a drop in voltage on the blue wire, it becomes a lower resistance for the green wire so more field current can flow. The increased flow causes a larger magnetic field to be produced in the field winding which results in increased output voltage which appears on the blue wire.
As with the regulator built into the Engine Computer, this external regulator has temperature compensation built in. That means it will raise the target system voltage a little bit in colder weather. Recharging the battery is a chemical process, and that process is not as efficient in colder weather. That's why charging voltage is increased slightly. It is decreased in hot weather to reduce the chances of boiling the water out of the battery.
Once the system is up and running, you might see the Check Engine light is turned on. The Engine Computer monitors that small field current to verify it is working properly. When the current doesn't flow through its internal circuitry, it will set a diagnostic fault code, "Field circuit not switching properly" in memory. Anything that can have an adverse effect on tail pipe emissions is supposed to turn the light on. Low system voltage affects injectors, ignition coils, and the fuel pump. If you find this to be the case, you can try connecting a resistor between the two wires you removed from the back of the alternator. That should mimic the resistance of the field winding and make the computer think it's doing something of value. A six to ten ohm resistor should work. Without doing the math, about a five watt resistor should work fine.
Thursday, May 27th, 2010 AT 4:51 PM