It's not a "command signal" in the manner you imply. An alternator requires an electrical current through the copper windings before it will begin to output electricity. For instance, you couldn't just spin the altnerator by hand to charge a dead battery. The windings need to have a current passed through them first. The dummy light acts as a resistive load that accomplishes that. You could just as easily install a small resistor in place of the dummy light to achieve the same effect of "starting" the alternator. Speaking of which, I know a lot of people have been replacing all of their dash, door and marker lights with LED's. If you replace the alternator dummy light with an LED, you'll need to install a resistor in-line with the LED because an LED is not enough of a resistive load to charge the alternator windings. I'm sure that this has been covered in the archives. Rich A. #5335 --- In dmcnews@xxxxxxxxxxxxxxx, "daviddelorean" <daviddelorean@...> wrote: > > Is there any truth to the theory that the light bulb in your > alternator tell tale light actually is responsible for "telling" your > alternator to begin generating power? I read this somewhere online and > can't figure it out. > 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/dmcnews Yahoo! 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! ID required) <*> To change settings via email: mailto:dmcnews-digest@xxxxxxxxxxxxxxx mailto:dmcnews-fullfeatured@xxxxxxxxxxxxxxx <*> To unsubscribe from this group, send an email to: dmcnews-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/