On all F150 models this wire is looped back to the stator/volt regulator ..
REGULATOR CIRCUIT TESTS
"S" Circuit With Ammeter
Connect positive voltmeter lead to regulator wiring plug "S" terminal position. Turn ignition on.
Voltmeter should indicate battery voltage. If there is no voltage, "S" wire lead from ignition switch is open. Repair and retest system.
"S" & "I" Circuit With Indicator Light
Disconnect regulator wiring plug, and install a jumper wire between "A" and "F" terminals. With engine idling, connect negative lead of voltmeter to ground. Connect positive voltmeter lead to "S" and then to "I" terminals of regulator wiring plug.
Voltage of "S" circuit should be 1/2 that of "I" circuit. If circuit tests are correct, install a new regulator. Remove jumper wire from regulator wiring plug. Connect plug to regulator and repeat CHARGING SYSTEM TESTING.
DIODE TEST (ON VEHICLE)
Disconnect electric choke (if equipped) and voltage regulator plug. Connect jumper wire between "A" and "F" terminals of voltage regulator wiring plug. Connect voltmeter to battery posts. Start and run engine at idle speed. Record voltmeter reading.
Move positive voltmeter lead to "S" terminal of alternator and note voltmeter reading. If meter reads 1/2 of battery voltage, alternator has an open positive diode. If meter reads about 1.0-1.5 volts more than 1/2 battery voltage, alternator has an open negative diode. Reconnect electric choke into circuit after test is completed.
UNDER VOLTAGE & FIELD CIRCUIT TESTS
To determine if jumping procedure is safe, field circuit should be checked with regulator wiring plug disconnected and ohmmeter connected from "F" terminal of wiring plug to battery ground. Ohmmeter should indicate 3-250 ohms. See Fig. 3 .
If load voltage did not increase 1/2 volt above base voltage, connect a jumper wire across "A" and "F" terminals of wiring plug and repeat test procedures.
If voltage is still under base voltage, remove jumper wire from wiring plug and leave plug disconnected from regulator. Connect jumper wire to "FLD" and "BAT" terminals on alternator and repeat test. If voltage increases 1/2 volt above battery voltage, repair wiring harness or replace regulator.
If low voltage is still indicated, stop engine. Move positive voltmeter lead to "BAT" terminal. If voltmeter now reads base voltage, repair alternator. If voltmeter reads zero volts, repair "BAT" wire or replace fusible link.
Monday, February 23rd, 2009 AT 3:26 PM