1 = Excitation, 2 = Voltage Sensor

Posted by John T on November 05, 2011 at 04:32:00 from (173.243.181.15):

In Reply to: Alternator posts 1 and 2 posted by equeen on November 04, 2011 at 20:24:37:

Im no alternator expert but if its similar to the Delco 10 SI family of internally regulated alternators heres what No 1 and No 2 terminals are for:

Of course, frame ground the case with the big main output stud wiring to the ammeter/battery:

SMALL SPADE TERMINALS 1 & 2

#1 Thats the external connection used to excite the alternator until such time (and RPM) that it becomes self excited....

That needs to be wired to a voltage source that becomes hot when the ignition switch is switched ON. So, where are such sources.

a) Well the IGN output of the ignition switch is a good source,,,,,,,,,,,

b) The same point electrically is where the wire down from the IGN switch wires to the high input (NOT to distributor) terminal on the ignition coil on non ballast resistor systems,,,,,,,,,,,

c) The same point electrically is where the wire down from the IGN switch wires to the high input (NOT to coil) side of a ballast resistor on ballasted systems

Soooooooo take your pick and wire the small No 1 terminal to any of the three locations listed above.

HOWEVER: It may happen that the tractor will still run after you turn off the ignition (alternator backfeeds coil) Sooooooooooo you fix that by installing a 10 ohm current limiting resistor in the wire from the source to the alternators No 1 terminal

ORRRRRRRRRRRRR some install a 3 to 5 amp 50 PIV or more diode in the line from the source to No 1 on the alternator (wire cathode band end towards alternator)

ORRRRRRRRRRRRR some install a small incandescent "idiot light" in that same line which prevents backfeed, limits current, and provides an indication of charging

# 2 Thats the voltage sensing terminal used to measure battery voltage so the regulation circuit can do its job. Many gents simply jump wire from No 1 up to the big main voltage output stud since thats "nearly" the same voltage as on the battery.

SUMMARY you can excite a GM 10 SI family of alternators by feeding off the input (NOT to coil) side of an external ballast resistor. However Id add a series 10 ohm resistor or a diode in that wiring to prevent backfeeding the ignition coil. Id wire the No 2 terminal to the big main output stud

IF THATS NOT THE ALTERNATOR YOU HAVE (GM 10 SI family) OR I MISSED ANYTHING HOPEFULLY THE OTHER FINE GENTS CAN ADD TO THIS

John T NOT an alternator expert

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