Hello, Just to clarify wording regarding the indicator light for the alternator. It serves two functions: 1. The primary function is to indicate that the alternator has malfunctioned. 2. The secondary function is get the alternator started generating power when required. Discussion of 1. The indicator lights when the ignition is on and the engine had not been started, and thus the alternator is not functioning OR when the engine is running and the alternator is not supplying power to the system (not functioning). The indicator is wired between the 12 V bus, which is supplied by the battery when the ignition is "on" and the field (rotating portion) of the alternator. As the field has little or no residual magnetism, the alternator will not supply power to the system at the time the engine starts. The regulator for the alternator is powered by the output of the alternator output but is isolated from the battery by diodes which will only allow power to go the regulator when the alternator is making some. Thus the second function: Discussion of 2. When the engine is first started, without the indicator to provide some small amount of current to "excite" the field, the alternator would not provide power to the system. When the field starts to have magnetism due to the excitation of the indicator lamp, then the regulator begins to function and control the field and thus the alternator's output! The field of the alternator has little or no residual magnetism. . Clarification of terms: The field of an alternator is the rotating element, and the armature is the wiring in the body of the alternator. As opposed to a generator where the field is the non rotating component, and the armature is rotating. Hence, alternators have brushes which contact slip rings, and generators have brushes which contact commutator rings (which act as rectifiers). Why this long discussion? The indicator light does not provide regulation for the alternator, and in fact is excluded by diodes from doing more than Function 1 once the engine is on and the alternator is functioning. I want to make clear that the engine will run for some time without the alternator (depending on the battery's condition and functions being used). Thus if the indicator lamp or bulb were not there at all, the engine would still start; it just would run for a long time, (depending on the electrical load and battery state) probably hours. Now as to the type of indicator. I have what papers to be a factory supplied Motorola alternator in my car and I have an LED indicator in the "alternator" position of my dashboard. I have driven the car for many thousands of miles under all kinds of battery load condition, without having to recharge the battery. Therefore I conclude that the Motorola alternator starts and will work fine with an LED in that situaton. That is to say, the relatively low current that can flow through the LED is sufficient to start generation. John H. and I have had lots of discussions about this with regard the extra power alternators which he sells. He claims that those alternators will not work with an LED in the indicator socket. I can't understand why not, but concede the point to him. A resistor to shunt the LED and thus provide sufficient current to excite the alternator might be a solution. But also defeat the purpose of the LED. Another couple of comments. The regulator for the alternator does not control the current output. It only controls the voltage output. This is fine, as the diodes isolate the alternator from the system if its voltage output is below the battery voltage. The only current regulation is provided by the resistance of the fixed armature windings. When the current output from the alternator increases, the resistance of the windings increases. At some point the regulator cannot provide enough field current to over come the armature loss. As I know that many of the people who look at this forum has other cars, some of which have generators for the charging supply. These devices were generally designed before the wide availability of solid state devices. Thus the generator is controlled by electro- mechanical means. Another way to look at the situation is that the generator is really and alternator which uses the commutator to convert the generated AC voltage to DC. I mention generators only because, they were self starting as the field winding was static and wound on a core which had residual magnetism. Thus when converting from positive to negative ground the field had to be "sparked" (thus polarizing the core correctly) to get the generator to be a source of power as opposed to a sink. Please refer comments and corrections directly to me so as to not take up forum time and space. Al Roberts twodelo2@xxxxxxxxxxxxx VIN 16049 ------------------------------------ To address comments privately to the moderating team, please address: moderators@xxxxxxxxxxx For more info on the list, tech articles, cars for sale see www.dmcnews.com To search the archives or view files, log in at http://groups.yahoo.com/group/dmcnewsYahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/dmcnews/ <*> Your email settings: Individual Email | Traditional <*> To change settings online go to: http://groups.yahoo.com/group/dmcnews/join (Yahoo! 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