Less than 1/4 amp through a charge light supplied to the excite terminal will excite the alternator, problem is if a charge light or resistor is not used, the alternator will full "field" where the rotor will draw 3+ amps from the 12V source. If using a diode inline which drops voltage a bit, the field current will still be above 2 amps. Only with a charge light or other resistor will the excite current be whatever the light or resistor flows. (usually about 1/4 amp)
I see it every time I put a repaired SI series alternator on my test stand which has a field current meter. An alternator being supplied 12V to the #1 excite terminal will draw 2-3 amps through the field rotor and regulator. Only when the alternator starts charging so the field current can be supplied by the diode trio, will the excite current draw on the #1 regulator terminal go to 0.
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Today's Featured Article - What Oil Should I Use? - by Francis Robinson. I keep seein this question pop up over and over again in discussion groups all over the web. As with many things there are often several right answers and a few wrong ones. Some purist I'm sure will disagree to no end with what I will tell you but most of us out here in the real world don't really care do we ? Some of them only bring their noses down out of the air long enough to look down them anyway. If you are like me you are only doing this old tractor stuff because you enjoy it. You
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