1999 Mercury Marquis alternater

Unplug regulator 3-wire harness connector. Connect jumper wire from harness "A" terminal to regulator "A" terminal. Connect another jumper wire from regulator "F" terminal screw to generator housing. With engine idling, connect voltmeter negative lead to battery ground terminal. Connect voltmeter positive lead first to "S" terminal and then to "I" terminal of regulator harness connector. Voltage at "S" terminal should be about 7 volts and about 14 vo lts at "I" terminal. If "S" terminal and "I" voltages are okay, replace voltage regulator. Repeat LOAD TEST. If "S" and "I" circuit voltages are not as specified, go to next step. If voltage is present at "S" terminal, but not 6-8 volts, replace generator. If no voltage is present at "S" terminal, disconnect one-wire connector ("S" terminal) on back of generator. Check voltage at single "S" terminal. If about 7 volts are present repair "S" circuit wiring. If no voltage is present at single "S" terminal, replace generator. If no voltage is present at "I" terminal, repair indicator light wiring circuit. Restore wiring connections and repeat LOAD TEST.