Charging System - Generators & Regulators: Diagnosis

TROUBLE SHOOTING

Note. For additional trouble shooting, see CHARGING SYSTEM - GENERAL TROUBLE SHOOTING article in GENERAL INFORMATION.

Verify customer's complaint. Ensure battery posts and cables are clean and tight. Inspect drive belt. Inspect battery junction box fuses No. 11 (15-amp) and mega fuse FB (120-amp) located near battery junction box. On vehicles with 3.0L Duratec engine, inspect central junction box fuse No. 16 (10-amp). On all models, ensure connections at generator, regulator and engine ground are clean and tight. If problem is found, repair as necessary. On vehicles with 3.0L Duratec engine, if problem is not found, repair by symptom. See SYMPTOM INDEX table under SYSTEM TESTS. On models with 2.0L Zetec engine, if problem is not found, perform self-diagnostics. See SELF-DIAGNOSTIC SYSTEM .

BATTERY DRAIN TEST

Note. Amperage draw will vary from vehicle to vehicle depending on equipment package. Compare to a comparable vehicle for reference. No production vehicle should have more than a 50 mA (0.050 amp) draw.

Ensure junction box/fuse panels are accessible without turning on interior and hood lights. Drive vehicle over 30 MPH for at least 5 minutes. Park vehicle and allow to sit with ignition off for at least 40 minutes to allow electronic modules to power down. Go to next step.
Connect a fused jumper wire between negative battery cable and negative battery post. Disconnect negative battery cable from negative battery post, without breaking the jumper wire connection to prevent modules from resetting. Go to next step. NOTE: It is very important that continuity is not broken between negative battery post and negative battery cable when disconnecting battery cable or connecting ammeter. If continuity is broken, go to step 1 .
Ensure ammeter is set to read milliamps with at least a 10 amp capability. Connect ammeter between negative battery cable and negative battery post. Remove fused jumper wire. Go to next step.
If excessive current draw is present (50 mA or more), pull fuses from battery/central junction box one at a time and note any current drop when each fuse is removed. DO NOT reinstall fuses until test is complete. Go to next step.
Check wiring diagrams for any circuits that run from battery without passing through battery/central junction box. Disconnect these circuits if current draw still exists. Repair appropriate circuits as necessary. See POWER DISTRIBUTION in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

GENERATOR LOAD TEST

Ensure drive belt is in good condition. Replace belt as necessary. If belt is okay, connect charging system load tester in accordance with manufacturer's instructions. Start and run engine at 2000 RPM, and apply load until generator output levels off. Generator amperage should be at least 58 amps with engine at 2000 RPM. Go to next step.
Turn A/C system on. Turn blower speed to high. Turn headlights on to high beams. Voltage should increase a minimum of .5 volts. If voltage is as specified, system is operating properly at this time. If voltage is not as specified, perform «GENERATOR NO-LOAD TEST»(ref-139334-S29142695642002043000000) .

GENERATOR NO-LOAD TEST

Connect a voltmeter positive lead to B+ terminal on generator and negative lead to ground. Start and run engine at 2000 RPM, with all accessories off. Read voltmeter when voltage stabilizes. Voltage should be 13-15 volts. If voltage is not as specified, go to next step.
On vehicles equipped with 2.0L Zetec engine, perform self-diagnostics. See «SELF-DIAGNOSTIC SYSTEM»(ref-139334-S03991237872002043000000) . On vehicles equipped with 3.0L Duratec engine, repair by symptom. See «SYMPTOM INDEX»(ref-139334-S12753125852002043000000) table under SYSTEM TESTS.

SELF-DIAGNOSTIC SYSTEM

Note. All diagnostic tests are written specifically for New Generation Star (NGS) tester. Most generic OBD-II compliant scan tools should be able to perform all test procedures.

DIAGNOSTIC FORMATS

QUICK TEST and SYSTEM TESTS are diagnostic formats used to test and service EEC-V system. QUICK TEST allows technician to identify concerns and retrieve Diagnostic Trouble Codes (DTC). SYSTEM TESTS are used to check circuits, sensors and actuators.

Before starting any SYSTEM TEST, follow all steps under QUICK TEST to determine appropriate system test to perform. If vehicle passes QUICK TEST and no driveability symptoms or intermittent faults exist, EEC-V system is okay.

DIAGNOSTIC TROUBLE CODES

During QUICK TEST, 3 types of Diagnostic Trouble Codes (DTCs) are retrieved and diagnosis must be performed in the following order: Key On Engine Off (KOEO), Key On Engine Running (KOER) and Continuous Memory DTCs. See QUICK TEST for self-test procedures. DTCs may be cleared from PCM memory after DTCs have been recorded or fault has been repaired. See CLEARING CODES . If fault is still present after clearing DTCs, fault will reset.

KOEO & KOER On-Demand Self-Test Codes

Record DTCs in order received. These DTCs indicate current faults in system and should be serviced in order of appearance. See DIAGNOSTIC TROUBLE CODE DEFINITIONS under QUICK TEST to identify appropriate system test to perform.

QUICK TEST

Quick Test is divided into 3 specialized test procedures that are functional tests of EEC-V system. All self-tests are completely menu driven using the New Generation Star (NGS) scan tool. The following procedures must be followed in sequence to avoid misdiagnosis

«VISUAL CHECK»(ref-139334-S16714120312004080400000)
«VEHICLE PREPARATION & EQUIPMENT HOOKUP»(ref-139334-S11184044062004080400000)
«KOEO ON-DEMAND SELF-TEST»(ref-139334-S30901000122004080400000)
«KOER ON-DEMAND SELF-TEST»(ref-139334-S24807374782004080400000)
«CONTINUOUS MEMORY SELF-TEST»(ref-139334-S00782665682004080400000)

Complete QUICK TEST before performing any system tests. Record any DTCs retrieved. Service DTCs in the following order: KOEO DTCs, KOER DTCs, then Continuous Memory DTCs and service first DTC output. If servicing Continuous Memory DTCs, retrieve any available freeze frame data. See FREEZE FRAME DATA MODE under ADDITIONAL SYSTEM FUNCTIONS in appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. Disregard any identical or related Continuous Memory DTCs if previously serviced. After each service or repair procedure has been completed, always repeat QUICK TEST procedures to ensure all EEC-V systems are working properly and DTCs are no longer present.

Performing Self-Test

To perform self-test, turn ignition switch to OFF position. Ensure test equipment is properly attached. Program scan tool using the following steps

Select VEHICLE & ENGINE SELECTION menu.
Select NEW VEHICLE, YEAR & MODEL.
Select DIAGNOSTIC DATA LINK.
Select POWERTRAIN CONTROL MODULE.
Select DIAGNOSTIC TEST MODE.
Select KOEO ON-DEMAND SELF-TEST.
Turn ignition switch to ON position.
Follow operating instructions from scan tool menu.
Record DTCs and perform appropriate system test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-139334-S29027861182004080400000) . After KOEO on-demand self-test is complete, cycle ignition switch before performing other self-tests or driving vehicle.

BPP, PSP & TCS Test Procedures

This test ensures EEC-V system is able to detect a change of state in brakelight switch, TCS and PSP switches. During KOER on-demand self-test, the brake pedal must be applied and then released, TCS must be cycled, and steering wheel must be turned at least 1/4 of a revolution.

Retrieve any available freeze frame data prior to self-test. See FREEZE FRAME DATA MODE under ADDITIONAL SYSTEM FUNCTIONS in appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. To perform self-test, turn ignition switch to OFF position. Ensure test equipment is properly attached. Program scan tool using the following steps

Select VEHICLE & ENGINE SELECTION menu.
Select NEW VEHICLE, YEAR & MODEL.
Select DIAGNOSTIC DATA LINK.
Select POWERTRAIN CONTROL MODULE.
Select DIAGNOSTIC TEST MODE.
Select RETRIEVE/CLEAR CONTINUOUS DTCs.
Turn ignition switch to ON position.
Follow operating instructions from scan tool menu.
Record DTCs and perform appropriate system test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-139334-S29027861182004080400000) . After continuous memory self-test is complete, cycle ignition switch before performing other self-tests or driving vehicle.

Select VEHICLE & ENGINE SELECTION menu.
Select NEW VEHICLE, YEAR & MODEL.
Select DIAGNOSTIC DATA LINK.
Select POWERTRAIN CONTROL MODULE.
Select DIAGNOSTIC TEST MODE.
Select RETRIEVE/CLEAR CONTINUOUS DTCs.
Turn ignition switch to ON position.
Follow operating instructions from scan tool menu.
Record DTCs and perform appropriate system test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-139334-S29027861182004080400000) . After continuous memory self-test is complete, cycle ignition switch before performing other self-tests or driving vehicle.

DIAGNOSTIC TROUBLE CODE DEFINITIONS

DTC (1)	Description	Perform Test
P1246	System Voltage Failure	A
(1) Codes listed in this table are only for testing covered in this article. For complete DTC listing, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

(1)	Codes listed in this table are only for testing covered in this article. For complete DTC listing, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.

POWERTRAIN CONTROL MODULE DIAGNOSTIC TROUBLE CODE INDEX

TEST A: BATTERY IS DISCHARGED OR VOLTAGE IS LOW

Note. Failure to fully charge battery before retesting may cause false readings.

Test battery condition. See «BATTERY DRAIN TEST»(ref-139334-S40275708612002043000000) under ON-VEHICLE TESTING. If battery is okay, go to next step. If battery is not okay, replace battery.
Perform generator load and no-load tests. See «GENERATOR LOAD TEST»(ref-139334-S02194870912002043000000) and «GENERATOR NO-LOAD TEST»(ref-139334-S29142695642002043000000) under ON-VEHICLE TESTING. If generator is okay, go to next step. If generator is not okay, perform «TEST B: WARNING INDICATOR IS ON WITH ENGINE RUNNING, SYSTEM IS NOT CHARGING (3.0L DURATEC)»(ref-139334-S21001343772002043000000) or «TEST C: WARNING INDICATOR IS ON WITH ENGINE RUNNING, SYSTEM IS NOT CHARGING (2.0L ZETEC)»(ref-139334-S41999732282002043000000) .
Perform «BATTERY DRAIN TEST»(ref-139334-S40275708612002043000000) under ON-VEHICLE TESTING. If no excessive current draw was not found, go to next step. If any excessive current draw was found, repair as necessary.
Perform «ELECTRONIC DRAINS WHICH SHUT OFF WHEN BATTERY CABLE IS DISCONNECTED»(ref-139334-S10289420862002043000000) under ON-VEHICLE TESTING. If there are any current drains that shut off when the battery is disconnected, repair as necessary. If no drains were found, perform «TEST B: WARNING INDICATOR IS ON WITH ENGINE RUNNING, SYSTEM IS NOT CHARGING (3.0L DURATEC)»(ref-139334-S21001343772002043000000) or «TEST C: WARNING INDICATOR IS ON WITH ENGINE RUNNING, SYSTEM IS NOT CHARGING (2.0L ZETEC)»(ref-139334-S41999732282002043000000) .

Scheme 1

Scheme 1: TEST B: WARNING INDICATOR IS ON WITH ENGINE RUNNING, SYSTEM IS NOT CHARGING (3.0L DURATEC)

Scheme 2

Measure voltage between ground and generator B+ terminal (Yellow/White wire). (Scheme 1) If battery voltage is present, go to next step. If battery voltage is not present, repair circuit between generator and battery.
Turn ignition switch to LOCK position. Disconnect generator 3-pin harness connector. Measure voltage between ground and generator connector harness terminal No. 3 (Black/Yellow wire). (Scheme 2) If battery voltage is present, go to next step. If battery voltage is not present, repair circuit between generator and battery.
Turn ignition switch to RUN position. Measure voltage between ground and generator harness connector terminal No. 1 (Light Green/Red wire). If battery voltage is present, go to next step. If battery voltage is not present, repair Light Green/Red wire between generator and instrument cluster. See «WIRING DIAGRAMS»(ref-139334-S01955244022002043000000).
Start engine and run at 2000 RPM. Measure voltage between positive battery terminal and generator terminal B+ (Yellow/White wire). (Scheme 1) If voltage is less than 0.5 volt, replace generator. If voltage is 0.5 volt or more, repair Yellow/White wire between generator and battery.

TEST C: WARNING INDICATOR IS ON WITH ENGINE RUNNING, SYSTEM IS NOT CHARGING (2.0L ZETEC)

Connect New Generation Star (NGS) tester to Data Link Connector (DLC). Turn ignition switch to RUN position. Using NGS tester, perform Powertrain Control Module (PCM) self-test. If no DTCs exist, go to next step. If any DTCs exist, perform appropriate test. See «POWERTRAIN CONTROL MODULE DIAGNOSTIC TROUBLE CODE INDEX»(ref-139334-S12069208652002043000000) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition switch to LOCK position. Disconnect NGS tester. Disconnect generator 3-pin harness connector. Turn ignition switch to RUN position. Measure voltage between ground and generator harness connector terminal No. 1 (Gray/Orange wire). (Scheme 2) If voltage is zero volts, go to next step. If voltage is not zero volts, go to step 4.
Turn ignition switch to LOCK position. Disconnect PCM 104-pin harness connector. Measure resistance in Gray/Orange wire between PCM harness connector terminal No. 59 and generator harness connector terminal No. 1. (Scheme 2)and (Scheme 3). If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, repair open in Gray/Orange wire between PCM and generator.
Connect generator harness connector. Perform «GENERATOR LOAD TEST»(ref-139334-S02194870912002043000000) under ON-VEHICLE TESTING. If generator is okay, go to next step. If generator is defective, replace generator.
Turn ignition switch to LOCK position. Disconnect PCM harness connector. Inspect connector for corrosion and pushed out pins. Connect PCM harness connector. Ensure connector is seated properly. Operate system. If problem still exists, replace PCM. If system is operating properly, problem may have been caused by a loose or corroded connector. Clear DTCs. Repeat PCM self-test.

Scheme 3

TEST D: SYSTEM OVERCHARGES, BATTERY VOLTAGE IS GREATER THAN 15.5 VOLTS (3.0L DURATEC)

Turn ignition switch to RUN position. Measure voltage between positive battery terminal and generator harness connector terminal No. 3 (Black/Yellow wire). (Scheme 2) If voltage is less than.5 volt, go to next step. If voltage is.5 volt or more, repair high resistance in Black/Yellow wire between generator and battery junction box.
Turn ignition switch to LOCK position. Inspect ground connections between voltage regulator, generator and engine, and battery and engine. If problem exists, repair connections as necessary. If all connections are clean and tight, replace generator.

TEST E: SYSTEM OVERCHARGES, BATTERY VOLTAGE IS GREATER THAN 15.5 VOLTS (2.0L ZETEC)

Connect New Generation Star (NGS) tester to Data Link Connector (DLC). Turn ignition switch to RUN position. Using NGS tester, perform Powertrain Control Module (PCM) self-test. If no DTCs exist, go to next step. If any DTCs exist, perform appropriate test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-139334-S29027861182004080400000) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition switch to LOCK position. Disconnect NGS tester. Start engine and let idle. Turn all accessories off. Measure voltage between battery terminals while varying engine speed. If voltage is less than 15 volts, system is operating correctly. If voltage is 15 volts or more, go to next step.
Turn ignition switch to LOCK position. Disconnect generator 3-pin harness connector. Start engine and let idle. Perform load and no-load tests on generator. See «GENERATOR LOAD TEST»(ref-139334-S02194870912002043000000) and «GENERATOR NO-LOAD TEST»(ref-139334-S29142695642002043000000) under ON-VEHICLE TESTING. If generator is okay, go to next step. If generator is defective, replace generator.
Turn ignition switch to LOCK position. Measure voltage between ground and generator harness connector terminal No. 3 (Black/Yellow wire). (Scheme 2) If voltage is less than 0.5 volt from battery voltage, replace generator. If voltage is not less than 0.5 volt from battery voltage, repair high resistance in Black/Yellow wire between generator and battery junction box.

TEST F: WARNING INDICATOR IS ON WITH ENGINE RUNNING, SYSTEM IS CHARGING (3.0L DURATEC)

Disconnect generator 3-pin harness connector. Turn ignition switch to RUN position. Check warning indicator. If warning indicator illuminates, repair short to ground in Light Green/Red wire between generator and instrument cluster. If warning indicator does not illuminate, replace generator.

TEST G: WARNING INDICATOR IS ON WITH ENGINE RUNNING, SYSTEM IS CHARGING (2.0L ZETEC)

Connect New Generation Star (NGS) tester to Data Link Connector (DLC). Turn ignition switch to RUN position. Using NGS tester, perform Powertrain Control Module (PCM) self-test. If no DTCs exist, go to next step. If any DTCs exist, perform appropriate test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-139334-S29027861182004080400000) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition switch to LOCK position. Disconnect NGS tester. Start engine and let idle. Turn all accessories off. Measure voltage between battery terminals while varying engine speed. If voltage is less than 15 volts, go to next step. If voltage is 15 volts or more, perform «TEST E: SYSTEM OVERCHARGES, BATTERY VOLTAGE IS GREATER THAN 15.5 VOLTS (2.0L ZETEC)»(ref-139334-S27538269662002043000000).
Turn ignition switch to LOCK position. Disconnect generator 3-pin harness connector. Turn ignition switch to RUN position. Measure voltage between ground and generator harness connector terminal No. 3 (Black/Yellow wire). (Scheme 2) If voltage is equal to battery voltage, go to next step. If voltage is not equal to battery voltage, repair Black/Yellow wire between generator and battery junction box.
Turn ignition switch to LOCK position. Disconnect PCM 104-pin harness connector. Measure resistance between ground and PCM harness connector terminal No. 59 (Gray/Orange wire). If resistance is 10 k/ohms or more, go to next step. If resistance is less than 10 k/ohms, repair short to ground in Gray/Orange wire between generator and PCM.
Connect PCM harness connector and generator harness connector. Perform load and no-load tests on generator. See «GENERATOR LOAD TEST»(ref-139334-S02194870912002043000000) and «GENERATOR NO-LOAD TEST»(ref-139334-S29142695642002043000000) under ON-VEHICLE TESTING. If generator is okay, go to next step. If generator is defective, replace generator.
Disconnect PCM harness connectors. Inspect connector for corrosion and pushed out pins. Connect PCM harness connector. Ensure connector is seated properly. Operate system. If problem still exists, replace PCM. If system is operating properly, problem may have been caused by a loose or corroded connector. Clear DTCs. Repeat PCM self-test.

TEST H: WARNING INDICATOR IS OFF WITH IGNITION SWITCH ON & ENGINE OFF (3.0L DURATEC)

Turn ignition switch to LOCK position. Disconnect generator 3-pin harness connector. Connect a fused jumper wire between ground and generator harness connector terminal No. 1 (Light Green/Red wire). (Scheme 2) Turn ignition switch to RUN position. If warning indicator illuminates, replace generator. If warning indicator does not illuminate, repair warning indicator problem as necessary. See appropriate ANALOG INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.

TEST I: WARNING INDICATOR IS OFF WITH IGNITION SWITCH ON & ENGINE OFF (2.0L ZETEC)

Connect New Generation Star (NGS) tester to Data Link Connector (DLC). Turn ignition switch to RUN position. Using NGS tester, perform Powertrain Control Module (PCM) self-test. If no DTCs exist, go to next step. If any DTCs exist, perform appropriate test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-139334-S29027861182004080400000) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition switch to LOCK position. Disconnect NGS tester. Disconnect generator 3-pin harness connector. Connect a fused (15-amp) jumper wire between ground and generator harness connector terminal No. 1 (Gray/Orange wire). (Scheme 2) Turn ignition switch to RUN position. If warning indicator does not illuminate, go to next step. If warning indicator illuminates, replace generator.
Disconnect PCM harness connector. Inspect connector for corrosion and pushed out pins. Connect PCM harness connector. Ensure connector is seated properly. Operate system. If problem still exists, replace PCM. If system is operating properly, problem may have been caused by a loose or corroded connector. Clear DTCs. Repeat PCM self-test.

TEST J: WARNING INDICATOR FLICKERS OR IS INTERMITTENT (3.0L DURATEC)

Inspect all generator, battery, and power distribution connections for looseness, corrosion, loose or bent terminals, or loose eyelets. If connections are clean and tight, go to next step. If problem exists, repair as necessary.
Start engine and let idle. Inspect battery junction box fuse No. 11 (15-amp) for looseness. Wiggle fuse and note warning indicator operation. If warning indicator does not flicker, go to next step. If warning indicator flickers, repair loose fuse connections.
Turn ignition switch to LOCK position. Connect a fused jumper wire between positive battery terminal and generator harness connector terminal No. 3 (Black/Yellow wire). (Scheme 2) Start engine and let idle. Note warning indicator operation. If warning indicator flickers, repair warning indicator problem as necessary. See appropriate ANALOG INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. If warning indicator does not flicker, repair loose connection(s) in circuits.

TEST K: WARNING INDICATOR FLICKERS OR IS INTERMITTENT (2.0L ZETEC)

Connect New Generation Star (NGS) tester to Data Link Connector (DLC). Turn ignition switch to RUN position. Using NGS tester, perform Powertrain Control Module (PCM) self-test. If no DTCs exist, go to next step. If any DTCs exist, perform appropriate test. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-139334-S29027861182004080400000) under SELF-DIAGNOSTIC SYSTEM.
Disconnect generator 3-pin harness connector. Inspect all generator, battery, and power distribution connections for looseness, corrosion, loose or bent terminals, or loose eyelets. Connect generator connector. If problem does not exist, go to next step. If problem exists, repair connections as necessary.
Start engine and let idle. Inspect battery junction box fuse No. 11 (15-amp) for looseness. Wiggling fuse and note warning indicator operation. If warning indicator does not flicker, go to next step. If warning indicator flickers, repair loose fuse connections as necessary.
Turn all accessories off. Measure voltage between battery terminals while varying engine speed. If voltage is less than 15 volts, go to next step. If voltage is 15 volts or more, perform «TEST E: SYSTEM OVERCHARGES, BATTERY VOLTAGE IS GREATER THAN 15.5 VOLTS (2.0L ZETEC)»(ref-139334-S27538269662002043000000).
Turn ignition switch to LOCK position. Disconnect generator 3-pin harness connector. Turn ignition switch to RUN position. Connect a fused jumper wire between ground and generator harness connector terminal No. 1 (Gray/Orange wire). (Scheme 2) If warning indicator illuminates, go to next step. If warning indicator does not illuminate, repair open in Gray/Orange wire between generator and PCM.
Turn ignition switch to LOCK position. Remove jumper wire. Connect generator harness connector. Turn ignition switch to RUN position. Observe warning indicator operation. If warning indicator does not illuminate, go to next step. If warning indicator illuminates, PCM is operating properly. Recheck generator circuits for intermittent shorts or opens.
Turn ignition switch to LOCK position. Disconnect PCM harness connector. Inspect connector for corrosion and pushed out pins. Connect PCM harness connector. Ensure connector is seated properly. Operate system. If problem still exists, replace PCM. If system is operating properly, problem may have been caused by a loose or corroded connector. Clear DTCs. Repeat PCM self-test.

TEST L: GENERATOR NOISY

Turn ignition switch to LOCK position. Check accessory drive belt for damage and correct installation. Check mounting brackets and pulleys for looseness and damage. If problem does not exist, go to next step. If problem exists, repair as necessary.
Check generator installation. Ensure all fasteners are tight. If problem does not exist, go to next step. If problem exists, repair as necessary.
Disconnect generator 3-pin harness connector. Start engine and let idle. Turn headlights on. Turn rear defogger on. Turn blower motor to high speed. If noise still exists, go to next step. If noise does not still exist, replace generator.
Turn ignition switch to LOCK position. Connect generator harness connector. Start engine and let idle. Turn all accessories off. Using a stethoscope, check generator for unusual mechanical noise. If generator is source of noise, replace generator. If generator is not source of noise, isolate noise and repair as necessary.

TEST M: RADIO INTERFERENCE

Start engine and let idle. Tune radio to station where interference is present. Turn ignition switch to LOCK position. Disconnect generator 3-pin harness connector. Start engine and let idle. If interference is still present, repair radio concern. If interference is not still present, replace generator.

Charging System - Generators & Regulators: Diagnosis Ford Escape I