Mechanics

ALTERNATOR

1994 Ford Escort

Electrical problem
1994 Ford Escort 4 cyl Front Wheel Drive Automatic 161000 miles

replaced battery and altenator, car still dies when running a load. Drains battery. Do I need to trace the wiring and replace?Need help or change the alternator again.
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Harvey t
February 1, 2009.



LOW OR NO CHARGE CONDITION
Unplug harness connector from regulator at rear of alternator. Connect ohmmeter between regulator "A" and "F" terminal screws. See Fig. 1 and Fig. 3 . If resistance is not greater than 2.4 ohms, a short in the field circuit or a grounded rotor coil is indicated. Replace alternator. If resistance is greater than 2.4 ohms, go to next step.
Reconnect regulator wiring plug. Connect negative voltmeter lead to ground. Contact positive voltmeter lead to regulator "A" terminal screw. If voltmeter does not indicate battery voltage, repair open or high resistance in "A" circuit wiring. Perform load test after repairs.
If battery voltage is indicated at "A" terminal screw, ensure ignition switch is in OFF position. Connect positive voltmeter lead to regulator "F" terminal screw. If battery voltage is present, go to step 4). If battery voltage is not present, replace alternator.
Turn ignition switch to ON position (engine off). With voltmeter negative lead to ground, contact positive lead of voltmeter to regulator "F" terminal screw. If voltmeter indicates 2 volts or less, go to next step. If voltage is greater than 2 volts, check circuit between "I" terminal and ignition switch. Repair if necessary. See "S" & "I" CIRCUIT TEST. If "I" circuit is okay, replace regulator. Perform LOAD TEST after repair.
Start engine and run at 2000 RPM with headlights on. Measure voltage at "B+" terminal of alternator and at alternator feed wire at starter relay. If voltage readings differ by more than 0.5 volt, repair high resistance or open in wire between "B+" terminal and junction near starter relay.
If alternator still does not charge sufficiently, connect a jumper wire from regulator "F" terminal screw and ground it to rear housing. If output voltage increases to 13-15 volts, replace regulator. If output voltage does not increase to at least 13 volts replace alternator.
"S" & "I" CIRCUIT TEST
Unplug regulator 3-wire harness connector. Connect jumper wire from harness "A" terminal to regulator "A" terminal. See Fig. 1 and Fig. 2 . Connect another jumper wire from regulator "F" terminal screw to alternator 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. See Fig. 2 . Voltage at "S" terminal should be about 7 volts and about 14 volts 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 between 6-8 volts, replace alternator. If no voltage is present at "S" terminal, disconnect one-wire connector ("S" terminal) on back of alternator. See Fig. 1 . Check voltage at single "S" terminal. If approximately 7 volts are present repair "S" circuit wiring. If no voltage is present at single "S" terminal, replace alternator.
If no voltage is present at "I" terminal, repair indicator light wiring circuit. Restore wiring connections and repeat LOAD TEST.
Fig. 2: Identifying Regulator Harness Connector Terminals
Courtesy of FORD MOTOR CO.
FIELD CIRCUIT DRAIN TEST
NOTE:Connect voltmeter negative lead to alternator rear housing for following voltage readings.

Turn ignition switch to OFF position. Connect voltmeter positive lead to regulator "F" terminal screw. Battery voltage should be present.
If less than battery voltage is present, unplug regulator harness connector. Connect voltmeter positive lead to harness connector "I" terminal. See Fig. 2 . If voltage is not present, go to next step. If voltage is present, repair wiring circuit "I" from ignition switch to eliminate voltage source.
Connect voltmeter positive lead to regulator wiring plug "S" terminal. If voltage is not present, replace regulator. If voltage is present, unplug alternator wiring connector.
Connect voltmeter positive lead to regulator wiring plug "S" terminal. If voltage is present, repair "S" terminal wiring circuit to alternator. If no voltage is present, replace alternator.


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Dave H
Feb 1, 2009.