Ford Mustang Quiz
Battery and Charging System

Pinpoint Tests

In this manual: Battery and Charging System
Service Information — 34Suspension — 63Driveline — 80Brake System — 74Steering System — 42Engine — 329Automatic Transmission — 84Manual Transmission, Clutch and Transfer Case — 64Exhaust System — 8Fuel System — 39Climate Control System — 76Instrumentation and Warning Systems — 25Battery and Charging System — 19Audio Systems — 14Lighting — 24Electrical Distribution — 8Electronic Feature Group — 11Body — 173Frame and Mounting — 6General Information — 1
~8min read

CAUTION: Do not make jumper connections except as directed. Incorrect connections may damage the voltage regulator test terminals, fuses, or fuse links.

CAUTION: Do not allow any metal object to come in contact with the generator housing and internal diode cooling fins.

NOTE: All voltage measurements are referenced to the negative (-) battery post unless otherwise specified.

PINPOINT TEST A: BATTERY IS DISCHARGED OR VOLTAGE IS LOW

Test Step Result / Action to Take
A1 CHECK BATTERY CONDITION Yes

GO to A2 .

No

INSTALL a new battery. REFER to Section. TEST the system for normal operation
  • Carry out the Battery-Condition Test to determine if the battery can hold a charge and is OK for use.
  • Is the battery OK?
A2 CHECK THE GENERATOR OUTPUT Yes

GO to A3 .

No

GO to Pinpoint Test B .
  • Carry out the On-Vehicle Generator Load/No Load Test. Refer to Component Tests in this section.
  • Is the generator OK?
A3 CHECK FOR CURRENT DRAINS Yes

REPAIR as necessary. TEST the system for normal operation.

No

GO to A4
  • Carry out the Battery-Drain Test. Refer to Component Tests in this section.
  • Are there any excessive current drains?
A4 CHECK FOR CURRENT DRAINS WHICH SHUT OFF WHEN THE BATTERY IS DISCONNECTED Yes

REPAIR as necessary. TEST the system for normal operation.

No

GO to Pinpoint Test B .
  • Carry out the Battery-Electronic Drains Which Shut Off When the Battery Cable is Disconnected Test.

    Refer to Component Tests in this section.

  • Are there any current drains which shut off when the battery is disconnected?

PINPOINT TEST B: THE CHARGING SYSTEM WARNING INDICATOR IS ON WITH THE ENGINE RUNNING (THE BATTERY VOLTAGE DOES NOT INCREASE)

Test Step Result / Action to Take
B1 CHECK GENERATOR B+ CIRCUIT 38 (BK/OG) Yes

GO to B2 .

No

REPAIR the circuit.

TEST the system for normal operation.
  • Disconnect: Generator B+ C102b.
  • Measure the voltage between the generator C102b, circuit 38 (BK/OG), component side and ground.
  • Is the voltage equal to battery positive voltage (B+)?
B2 CHECK GENERATOR A CIRCUIT 36 (YE/WH) Yes

GO to B3 .

No

REPAIR the circuit.

TEST the system for normal operation.
  • Disconnect: Generator C102c (4.6L 4V) or C102a (3.8L or 4.6L 2V).
  • Measure the voltage between the generator C102c (4.6L 4V) or C102a (3.8L or 4.6L 2V) pin 3, circuit 36 (YE/WH), harness side and ground.
  • Is the voltage equal to battery positive voltage (B+)?
B3 CHECK I CIRCUIT 904 (LG/RD) FOR AN OPEN Yes

GO to B4 .

No

REPAIR the circuit.

TEST the system for normal operation.
  • Key in ON position.
  • With the ignition switch in the RUN position and the engine off, measure the voltage between the generator C102c (4.6L 4V) or C102a (3.8L or 4.6L 2V) pin 1, circuit 904 (LG/RD), harness side and ground.
  • Is the voltage equal to battery positive voltage (B+)?
B4 CHECK FOR VOLTAGE DROP IN B+ CIRCUIT 38 (YE/WH) Yes

INSTALL a new generator. REFER to Section .

TEST the system for normal operation.

No

REPAIR high resistance in the B+ circuit 38 (BK/OG).

TEST the system for normal operation.
  • Key in START position.
  • With the engine at 2,000 rpm, measure the voltage drop between the generator C102b, circuit 38 (BK/OG), component side and positive battery terminal
  • Is the voltage drop less than 0.5 volt?

PINPOINT TEST C: THE SYSTEM OVERCHARGES (THE BATTERY VOLTAGE IS GREATER THAN 15.5 VOLTS)

Test Step Result / Action to Take
C1 CHECK FOR VOLTAGE DROP IN A CIRCUIT 36 (YE/WH) Yes

GO to C2 .

No

REPAIR the high resistance in A circuit 36 (YE/WH). TEST the system for normal operation.
  • Disconnect: Generator C102c (4.6L 4V) or C102a (3.8L or 4.6L 2V).
  • Key in ON position.
  • Measure the voltage drop between the generator C102c (4.6L 4V) or C102a (3.8L or 4.6L 2V) pin 3, circuit 36 (YE/WH), harness side and positive battery terminal.
  • Is the voltage drop less than 0.5 volt?
C2 CHECK GENERATOR AND BATTERY GROUND CONNECTIONS Yes

INSTALL a new generator. REFER to Section. TEST the system for normal operation.

No

REPAIR ground connections as necessary. TEST the system for normal operation.
  • Key in OFF position.
  • Check the ground connections between the voltage regulator and the generator and the engine, and the battery and the engine.
  • Are all ground connections clean and tight?

PINPOINT TEST D: THE CHARGING SYSTEM WARNING INDICATOR IS ON WITH THE ENGINE RUNNING AND THE BATTERY INCREASES VOLTAGE

Test Step Result / Action to Take
D1 CHECK I CIRCUIT 904 (LG/RD) FOR A SHORT TO GROUND Yes

REPAIR circuit 904 (LG/RD) for a short to ground. TEST the system for normal operation.

No

INSTALL a new generator. REFER to Section. TEST the system for normal operation.
  • Disconnect: Generator C102c (4.6L 4V) or C102a (3.8L or 4.6L 2V).
  • Key in ON position.
  • With the ignition switch in the RUN position, check the charging system warning indicator.
  • Is the charging system warning indicator illuminated?

PINPOINT TEST E: THE CHARGING SYSTEM WARNING INDICATOR IS OFF WITH THE IGNITION SWITCH IN THE RUN POSITION AND THE ENGINE OFF

Test Step Result / Action to Take
E1 CHECK THE CHARGING SYSTEM WARNING INDICATOR LAMP Yes

INSTALL a new generator. REFER to Section. TEST the system for normal operation.

No

REFER to Section for diagnosis and testing of the instrument cluster
  • Disconnect: Generator C102c (4.6L 4V) or C102a (3.8L or 4.6L 2V).
  • With the engine off, connect a fused (15A) jumper wire between the generator C102c (4.6L 4V) or C102a (3.8L or 4.6L 2V) pin 1, circuit 904 (LG/RD), harness side and ground.
  • Key in ON position.
  • Is the charging system warning indicator lamp illuminated?

PINPOINT TEST F: THE CHARGING SYSTEM WARNING INDICATOR LAMP FLICKERS OR IS INTERMITTENT

Test Step Result / Action to Take
F1 CHECK FOR LOOSE CONNECTIONS Yes

GO to F2 .

No

REPAIR as necessary. TEST the system for normal operation.
  • Check all generator, battery, and power distribution connections for looseness, corrosion, loose or bent terminals, or loose eyelets.
  • Are all connections clean and tight?
F2 CHECK FUSE Yes

REPAIR loose fuse connections as necessary. TEST the system for normal operation.

No

GO to F3 .
  • Key in START position.
  • With the engine running, check battery junction box (BJB) fuse 20 (20A) in circuit 36 (YE/WH) for looseness by wiggling the fuse and noting the charging system warning indicator lamp operation.
  • Does the charging system warning indicator lamp flicker?
F3 CHECK A CIRCUIT 36 (YE/WH) CONNECTIONS Yes

REFER to Section. TEST the system for normal operation.

No

REPAIR loose connection(s) in circuits. TEST the system for normal operation.
  • Key in OFF position.
  • Connect a fused jumper wire between the generator C102c, (4.6L 4V) or C102a (3.8L or 4.6L 2V) pin 3, circuit 36 (YE/WH), harness side and the positive battery terminal
  • Key in START position.
  • With the engine running, note the charging system warning indicator operation.
  • Does the charging system warning indicator lamp flicker?

PINPOINT TEST G: THE GENERATOR IS NOISY

Test Step Result / Action to Take
G1 CHECK FOR ACCESSORY DRIVE NOISE Yes

GO to G2 .

No

REPAIR as necessary. REFER to Section for diagnosis and testing of the accessory drive system. TEST the system for normal operation.
  • Check the accessory drive belt for damage and correct installation. Check the accessory mounting brackets and generator pulley for looseness or misalignment.
  • Is the accessory drive OK?
G2 CHECK GENERATOR MOUNTING Yes

GO to G3 .

No

REPAIR as necessary. TEST the system for normal operation.
  • Check the generator mounting for loose bolts or misalignment.
  • Is the generator mounted correctly?
G3 CHECK GENERATOR FOR ELECTRICAL NOISE Yes

GO to G4 .

No

INSTALL a new generator. REFER to Section. TEST the system for normal operation.
  • Disconnect: Generator C102c (4.6L 4V) or C102a (3.8L or 4.6L 2V).
  • Key in START position.
  • With the engine running, turn the headlights on, rear defroster on, and the blower motor to the HI position.
  • Is the noise still present?
G4 CHECK GENERATOR FOR MECHANICAL NOISE Yes

INSTALL a new generator. REFER to Section. TEST the system for normal operation.

No

REFER to Section to diagnose the source of engine noise.
  • Key in OFF position.
  • Connect: Generator C102c (4.6L 4V) or C102a (3.8L or 4.6L 2V).
  • Key in START position.
  • Turn all accessories off. With the engine running, use a stethoscope or equivalent listening device to probe the generator for unusual mechanical noise.
  • Is the generator the noise source?

PINPOINT TEST H: RADIO INTERFERENCE

Test Step Result / Action to Take
H1 VERIFY GENERATOR IS SOURCE OF RADIO INTERFERENCE Yes

REFER to Section for diagnosis and testing of the in-vehicle entertainment system.

No

INSTALL a new generator. REFER to Section. TEST the system for normal operation.
  • Key in START position.
  • With the engine running, tune the radio to a station where the interference is present.
  • Key in OFF position.
  • Disconnect: Generator C102c (4.6L 4V) or C102a (3.8L or 4.6L 2V).
  • Key in START position.
  • With the engine running, note any radio interference.
  • Is the interference present with the generator disconnected?

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