1996 Bronco/F-Series

Section 14-00: Battery and Charging System, Service

1996 F-150, F-250, F-350, F-Super Duty and Bronco Workshop Manual

DIAGNOSIS AND TESTING

Pinpoint Tests

PINPOINT TEST A: SYSTEM DOES NOT CHARGE

A1 CHECK BATTERY CONNECTIONS

Inspect the battery positive and negative battery cables for loose or corroded connections.

Are the battery cables clean and tight?

Yes	No
GO to A2.	CLEAN and/or TIGHTEN the battery cables.

A2 CHECK DRIVE BELT TENSION

Examine drive belt for damage.
Perform the drive belt adjustment procedure. Refer to Section 03-05.

Is drive belt adjusted properly?

Yes	No
GO to A3.	ADJUST or REPLACE the drive belt.

A3 CHECK BATTERY

Perform the battery component tests. Refer to Component Tests in the Diagnosis and Testing portion of this section.

Is the battery OK?

Yes	No
PERFORM the generator component tests. REFER to Component Tests in the Diagnosis and Testing portion of this section.	REPLACE battery.

PINPOINT TEST B: SYSTEM OVERCHARGES (BATTERY BOILS OVER)

B1 CHECK VOLTAGE DROP IN A CIRCUIT

Key to RUN.
Measure voltage between test point A on the voltage regulator and the positive (+) battery post.

Is voltage drop less than 0.25 V?

Yes	No
GO to B2.	SERVICE excess voltage drop in Circuit 36 (Y/W). CHECK fuse and connectors in Circuit 36 and SERVICE as required.

B2 CHECK VOLTAGE DROP IN I CIRCUIT

Measure voltage at wiring harness I terminal, Circuit 904 (LG/R).

NOTE: Voltage regulator must be connected to wiring harness for this test.

Is voltage greater than 1 V?

Yes	No
GO to B3.	SERVICE high resistance in Circuit 904 (LG/R).

B3 CHECK FOR POOR GROUNDS

Check for poor ground connections between voltage regulator and generator, generator and engine, or engine and battery.

Are all ground connections clean and tight?

Yes	No
GO to B4.	CLEAN or SERVICE grounds as required.

B4 CHECK FOR FIELD CIRCUIT VOLTAGE

Key off.
Measure voltage at test point F on the voltage regulator (reference ground).

Is voltage at test point F equal to battery voltage?

Yes	No
Generator is OK. REPLACE voltage regulator.	GO to B5.

B5 CHECK FOR GROUNDED SLIP RING

Remove generator from vehicle.
Remove voltage regulator.
Measure resistance from each generator slip ring to the generator housing.

Is resistance from either slip ring to housing less than 200 ohms?

Yes	No
If grease or dirt has accumulated near the slip rings, CLEAN the slip rings and RECHECK resistance. If still less than 200 ohms, REPLACE generator.	REPLACE voltage regulator.

PINPOINT TEST C: INDICATOR LAMP STAYS ON, ENGINE RUNNING

C1 CHECK FOR OPEN A CIRCUIT

Measure voltage at test point A on the voltage regulator.

Is voltage at test point A equal to battery voltage?

Yes	No
GO to C2.	CHECK fuse in Circuit 36 (Y/W) and REPLACE if required. If OK, SERVICE open in Circuit 36 (Y/W).

C2 CHECK FOR SHORTED I CIRCUIT

Remove three-pin generator regulator connector.
Key to RUN.

Is indicator lamp on?

Yes	No
SERVICE short to ground in Circuit 904 (LG/R).	GO to C3.

C3 CHECK S CIRCUIT FUNCTION

Install generator regulator connector.
Remove one-pin S connector.
Connect wiring harness S terminal, Circuit 4 (W/BK) to the positive (+) battery post using a jumper wire.

Is indicator lamp on?

Yes	No
REMOVE jumper wire. GO to C4.	REMOVE jumper wire. GO to C5.

C4 CHECK FOR OPEN S CIRCUIT

Remove three-pin generator regulator connector.
Measure wiring resistance between the one-pin S connector and the S (center) pin of the generator regulator connector.

Is resistance greater than 1 ohm?

Yes	No
SERVICE open or excess resistance in Circuit 4 (W/BK).	CHECK for loose or bent pin in voltage regulator or connector. If OK, REPLACE voltage regulator.

C5 CHECK STATOR OUTPUT VOLTAGE

Start engine.
Measure voltage at the S terminal on the back of the generator.

Is voltage at least 1/2 of battery voltage?

Yes	No
GO to C6.	GO to Pinpoint Test N to find the cause of low generator output.

C6 CHECK GENERATOR OUTPUT VOLTAGE

Measure voltage at the B+ terminal on the back of the generator with the engine running at 2000 rpm and all accessories turned OFF.

Is voltage greater than 15.5 V?

Yes	No
GO to B1 to find the cause of high output voltage.	REPLACE voltage regulator.

PINPOINT TEST D: INDICATOR LAMP STAYS ON, IGNITION SWITCH OFF

D1 CHECK LAMP CIRCUIT WIRING

Key off.
Remove three-pin generator regulator connector.
Measure voltage at wiring harness I terminal, Circuit 904 (LG/R).

Is voltage greater than 0 V?

Yes	No
SERVICE Circuit 16 (R/LG). Circuit should be hot in RUN position only.	SERVICE instrument cluster. REFER to Section 13-01.

PINPOINT TEST E: INDICATOR LAMP DOES NOT COME ON

E1 CHECK FOR OPEN I CIRCUIT

Remove three-pin generator regulator connector.
Key to RUN.
Measure voltage at wiring harness I terminal, Circuit 904 (LG/R).

Is voltage greater than 0 V?

Yes	No
GO to E2.	SERVICE open in Circuit 904 (LG/R).

E2 CHECK FOR DAMAGED CHARGE INDICATOR

Connect wiring harness I terminal, Circuit 904 (LG/R) to ground with a jumper wire.

Is indicator lamp on?

Yes	No
REMOVE jumper wire. GO to E3.	REPLACE charge indicator or SERVICE high resistance in lamp socket or Circuit 904 (LG/R).

E3 CHECK FOR POOR GROUNDS

Check for poor ground connections between voltage regulator and generator, generator and engine, or engine and battery.

Are all ground connections clean and tight?

Yes	No
GO to E4.	CLEAN or SERVICE grounds as required.

E4 CHECK S CIRCUIT WIRING

Remove one-pin S connector from generator.
Measure voltage at wiring harness S terminal, Circuit 4 (W/BK).

Is voltage greater than 0 V?

Yes	No
SERVICE Circuit 4 (W/BK). Circuit should be HOT only when engine is running. CHECK for swapped wires in generator voltage connector.	GO to E5.

E5 CHECK FOR SHORTED RECTIFIER

Measure voltage at the S terminal on the back of the generator.

Is voltage greater than 1 V?

Yes	No
If lamp is on with one-pin S connector removed, REPLACE generator.	REPLACE voltage regulator.

PINPOINT TEST F: INDICATOR LAMP FLICKERS/INTERMITTENT

F1 CHECK FOR LOOSE CONNECTIONS

Check these connections for corrosion, loose or bent pins, or loose eyelets:

Three-pin generator regulator connector.
One-pin S connector.
Generator B+ eyelet.
Power distribution box eyelets.
Battery cables.

Are all connections clean and tight?

Yes	No
GO to F2.	CLEAN or SERVICE connections as required.

F2 CHECK FOR FIELD CIRCUIT DRAIN

Key off.
Measure voltage at test point F on the voltage regulator.

Is voltage at test point F equal to battery voltage?

Yes	No
GO to F3.	GO to F5.

F3 CHECK FOR LOOSE A CIRCUIT FUSE

Start engine.
Check the generator fuse in the power distribution box for a loose connection by wiggling the fuse with the engine running.

Does indicator lamp flicker?

Yes	No
SERVICE loose fuse connection.	GO to F4.

F4 CHECK A CIRCUIT CONNECTIONS

With engine running, connect test point A on the voltage regulator to the positive (+) battery post using a jumper wire.

Does indicator lamp flicker?

Yes	No
REPLACE voltage regulator. If concern still exists, REPLACE generator.	SERVICE poor connection in Circuit 36 (Y/W).

F5 CHECK BRUSH HOLDER SCREWS

Remove generator from vehicle.
Check the brush holder screws, located on the voltage regulator (test points F and A).

Are the brush holder screws tight?

Yes	No
GO to F6.	TIGHTEN screws to 2.8-4.0 Nm (25-35 lb-in).

F6 CHECK FOR GROUNDED SLIP RING

Remove voltage regulator.
Measure resistance from each generator slip ring to the generator housing.

Is resistance from either slip ring to housing less than 200 ohms?

Yes	No
If grease or dirt has accumulated near the slip rings, CLEAN the slip rings and RECHECK resistance. If still less than 200 ohms, REPLACE generator.	REPLACE voltage regulator.

PINPOINT TEST G: BATTERY VOLTAGE GAUGE READS HIGH

G1 GENERATOR CHECK

Perform generator component test. Refer to Component Tests in the Diagnosis and Testing portion of this section.

Is the generator OK?

Yes	No
GO to G2.	GO to B1.

G2 CHECK INSTRUMENT CLUSTER CIRCUIT (LOW)

Key off.
Disconnect and remove the instrument cluster.
Measure the resistance on Pin 14 and Pin 1.
The resistance should read within a 475-525 ohm range.

Does the resistance read low?

Yes	No
REPLACE damaged charge indicator gauge (part of oil pressure gauge).	System OK.

PINPOINT TEST H: VOLTAGE GAUGE READS LOW

H1 CHECK GENERATOR

Perform generator component test. Refer to Component Tests in the Diagnosis and Testing portion of this section.

Is the generator OK?

Yes	No
GO to H2.	GO to A1.

H2 CHECK INSTRUMENT CLUSTER CIRCUIT (HIGH)

Key off.
Disconnect and remove the instrument cluster.
Measure the resistance on Pin 14 and Pin 1.
The resistance should read within a 475-525 ohm range.

Does the resistance read high?

Yes	No
REPLACE damaged charge indicator gauge (part of oil pressure gauge).	System OK.

PINPOINT TEST J: GENERATOR NOISY

J1 CHECK FOR ACCESSORY DRIVE NOISE

Using Rotunda Belt Tension Gauge 014-R1056 or equivalent, check the drive belt to make sure that it is installed properly and is not damaged. Refer to Section 03-05.
Check the accessory mounting brackets for loose bolts or misalignment condition.
Check for a bent pulley.

Is accessory drive OK?

Yes	No
GO to J2.	GO to Section 03-05 and SERVICE accessory drive as required.

J2 SUBSTITUTE KNOWN GOOD GENERATOR

Remove generator and replace with a known good generator.

Is noise present with a known good generator?

Yes	No
Generator is OK. INSTALL original generator. CHECK other accessories to find the cause of the noise.	REPLACE generator.

PINPOINT TEST K: RADIO INTERFERENCE

K1 VERIFY RADIO INTERFERENCE

Start engine.
Tune radio to a station where interference is present.
Remove three-pin generator regulator connector.

Is interference present with connector removed?

Yes	No
Generator is OK. REFER to Section 15-00 to find the cause of the radio interference.	GO to K2.

K2 SUBSTITUTE KNOWN GOOD GENERATOR

Remove generator and replace with a known good generator.

Is interference present with known good generator?

Yes	No
Generator is OK. REFER to Section 15-00 to find the cause of the radio interference.	REPLACE generator.

PINPOINT TEST L: BATTERY DOES NOT HOLD A CHARGE

L1 CHECK BATTERY CONNECTIONS

Inspect the battery cables for loose or corroded connections.

Are the battery cables clean and tight?

Yes	No
GO to L2.	CLEAN AND TIGHTEN the battery cables.

L2 CHECK DRIVE BELT TENSION

Perform the drive belt adjustment procedure. Refer to Section 03-05.

Is the drive belt adjusted properly?

Yes	No
GO to L3.	ADJUST or REPLACE the drive belt.

L3 LOOSE BATTERY POST

Check for loose battery posts.

Are posts OK?

Yes	No
GO to L4.	REPLACE battery.

L4 CRACKED BATTERY COVER

Remove battery hold down clamps and shields.
Check for broken/cracked case or battery cover.

Are case and cover OK?

Yes	No
GO to L5.	REPLACE battery.

L5 CHECK BATTERY

Perform the battery capacity test. Refer to Component Tests in the Diagnosis and Testing portion of this section.

Is battery OK?

Yes	No
GO to L6.	REPLACE the battery.

L6 CHECK FOR KEY-OFF DRAIN

Perform battery drain test. Refer to Component Tests in the Diagnosis and Testing portion of this section.

Is correct drain less than 50 Ma (or test lamp off)?

Yes	No
GO to L7.	GO to Component Tests in the Diagnosis and Testing portion of this section to find the cause of key-off battery drain.

L7 CHECK FOR OPEN B+ CIRCUIT

Measure voltage at B+ terminal on the back of the generator, Circuit 38 (BK/O).

Is voltage at B+ terminal equal to battery voltage?

Yes	No
GO to L8.	CHECK fuse link in Circuit 38 and REPLACE if required. If OK, SERVICE open in Circuit 38 (BK/O).

L8 CHECK FOR OPEN A CIRCUIT

Measure voltage at test point A on the voltage regulator.

Is voltage at test point A equal to battery voltage?

Yes	No
GO to L9.	CHECK fuse in Circuit 36 and REPLACE if required. If OK, SERVICE open in Circuit 36 (Y/W).

L9 CHECK FOR OPEN FIELD CIRCUIT

Measure voltage at test point F on the voltage regulator.

Is voltage at test point F equal to battery voltage?

Yes	No
GO to L10.	GO to L16.

L10 CHECK FOR OPEN I CIRCUIT

Key to RUN.
Measure voltage at wiring harness I terminal, Circuit 904 (LG/R).

NOTE: Voltage regulator must be connected to wiring harness for this test.

Is voltage greater than 1 V?

Yes	No
GO to L11.	SERVICE open or high resistance in Circuit 904 (LG/R).

L11 CHECK VOLTAGE DROP IN A CIRCUIT

Measure voltage drop between test point A on the voltage regulator and the positive (+) battery post.

Is voltage drop less than 0.25 V?

Yes	No
GO to L12.	SERVICE excess voltage drop in Circuit 36 (Y/W). CHECK fuse and connectors in Circuit 36 and SERVICE as required.

L12 CHECK FIELD TURN-ON

Measure voltage at test point F on the voltage regulator.

Is voltage at test point F less than 2 V?

Yes	No
GO to L13.	GO to L16.

L13 CHECK FOR SHORTED RECTIFIER

Remove one-pin S connector from generator.
Measure voltage between the S terminal on the back of the generator and ground.
Measure voltage between the positive (+) battery terminal and the S terminal on the back of the generator.

Is either voltage reading greater than 1 V?

Yes	No
REPLACE generator.	GO to L14.

L14 CHECK VOLTAGE DROP IN B+ CIRCUIT

Install S connector.
Start engine.
Turn headlights ON and HIGH blower.
With engine running at 2000 rpm, measure voltage drop between the B+ terminal on the back of the generator and the positive (+) battery post.

Is voltage drop less than 0.5 V?

Yes	No
GO to L15.	SERVICE excess voltage drop in Circuit 38 (BK/O). CHECK fuse link in Circuit 38 and the connections between the battery and power distribution box.

L15 CHECK FOR OPEN STATOR PHASE

Connect test point F on the voltage regulator to the negative (-) battery post using a jumper wire.
Perform Generator No-Load Test. Refer to Component Tests in the Diagnosis and Testing portion of this section.

Is generator output greater than the minimum output specified?

Yes	No
REPLACE voltage regulator.	REPLACE generator.

L16 CHECK FOR OPEN/SHORTED FIELD

Remove generator from vehicle.
Remove voltage regulator.
Measure resistance between the generator slip rings.

Is resistance greater than 10 ohms or less than 1 ohm?

Yes	No
REPLACE generator.	CHECK for worn brushes (less than 8mm long) or open brush leads and REPLACE if required. If OK, REPLACE voltage regulator.

PINPOINT TEST M: SYSTEM DOES NOT CHARGE 215 AMPERE GENERATOR

M1 CHECK BATTERY CONNECTIONS

Check the battery ground cables for loose or corroded connections.

Are the battery connections clean and tight?

Yes	No
GO to M2.	CLEAN or TIGHTEN the battery ground cables.

M2 CHECK DRIVE BELT

Check the drive belt for damage or improper tension. Refer to Section 03-05.

Is the drive belt OK?

Yes	No
GO to M3.	ADJUST or REPLACE the drive belt.

M3 CHECK BATTERIES

Perform the battery capacity test. Refer to Component Tests in the Diagnosis and Testing portion of this section.

Are the batteries OK?

Yes	No
GO to M4.	REPLACE defective battery.

M4 CHECK FOR BATTERY DRAIN

Perform the battery drain test. Refer to Component Tests in the Diagnosis and Testing portion of this section.

NOTE: Disconnect the negative (-) terminal of one of the batteries.

Is current drain less than 200 mA (or test lamp off)?

Yes	No
GO to M5.	LOCATE battery drain and SERVICE as required.

M5 CHECK FOR OPEN B+ CIRCUIT

Connect both batteries.
Measure voltage at B+ terminal on the back of the generator.

Is voltage at B+ terminal equal to battery voltage?

Yes	No
GO to M6.	CHECK megafuse in B+ circuit and REPLACE if required. If OK, REPAIR open circuit in B+ wiring.

M6 CHECK FOR OPEN A CIRCUIT

Remove voltage regulator connector.
Measure voltage at wiring harness A terminal.

Is voltage at A terminal equal to battery voltage?

Yes	No
GO to M7.	CHECK fuse in A circuit and REPLACE if required. If OK, REPAIR open circuit in A wiring.

M7 CHECK FOR OPEN I CIRCUIT

Install voltage regulator connector.
Key to RUN.
Measure voltage at wiring harness I terminal.

Is voltage greater than 1 V?

Yes	No
GO to M8.	REPAIR open circuit or high resistance in I wiring.

M8 CHECK VOLTAGE DROP IN B+ CIRCUIT

Start engine.
Turn headlights on and set blower motor switch on HI.
Increase engine speed to 2000 rpm and measure voltage drop between the B+ terminal on the back of the generator and the positive (+) battery post.

Is voltage drop less than 0.5 V?

Yes	No
REPLACE generator rear assembly.	REPAIR cause of voltage drop pin B+ circuit. CHECK the megafuse in B+ circuit and the connections at the battery and underhood fuse box.

PINPOINT TEST N: SYSTEM OVERCHARGES (BATTERY BOILS OVER)

N1 CHECK FOR OPEN A CIRCUIT

Remove voltage regulator connector.
Measure voltage at wiring harness A terminal.

Is voltage at A terminal equal to battery voltage?

Yes	No
GO to N2.	CHECK fuse in A circuit and REPLACE if required. If OK, REPAIR open circuit in A wiring.

N2 CHECK FOR POOR GROUNDS

Check for poor ground connections between generator and engine, or engine and battery.

Are all ground connections clean and tight?

Yes	No
REPLACE generator.	CLEAN or REPAIR grounds as required.

PINPOINT TEST P: INDICATOR LAMP STAYS ON, ENGINE RUNNING

P1 CHECK FOR OPEN B+ CIRCUIT

Measure voltage at B+ terminal on the back of the generator.

Is voltage at B+ terminal equal to battery voltage?

Yes	No
GO to P2.	CHECK the megafuse in B+ circuit and REPLACE if required. If OK, REPAIR open circuit in B+ wiring.

P2 CHECK FOR OPEN A CIRCUIT

Remove voltage regulator connector.
Measure voltage at wiring harness A terminal.

Is voltage at A terminal equal to battery voltage?

Yes	No
GO to P3.	CHECK fuse in A circuit and REPLACE if required. IF OK, REPAIR open circuit in A wiring.

P3 CHECK FOR SHORTED I CIRCUIT

Key to run with voltage regulator connector removed.

Is indicator lamp on?

Yes	No
REPAIR short circuit in I wiring.	GO to P4.

P4 CHECK GENERATOR OUTPUT VOLTAGE

Install voltage regulator connector.
Start engine.
Turn off all electrical accessories.
Increase engine speed to 2000 rpm and measure battery voltage.

Is voltage greater than 15.5 V?

Yes	No
GO to Pinpoint Test N to find the cause of high output voltage.	REPLACE generator rear assembly.

PINPOINT TEST Q: INDICATOR LAMP DOES NOT COME ON

Q1 CHECK FOR OPEN I CIRCUIT

Remove voltage regulator connector.
Key to RUN.
Measure voltage at wiring harness I terminal.

Is voltage greater than 0 V?

Yes	No
GO to Q2.	REPAIR open circuit in I wiring.

Q2 CHECK FOR BURNED-OUT BULB

Connect wiring harness I terminal to ground with a jumper wire.

Is indicator lamp on?

Yes	No
REMOVE jumper wire. GO to Q3.	REPLACE lamp or REPAIR poor connection in lamp socket.

Q3 CHECK FOR POOR GROUND

Check for a poor ground connection between generator and engine or engine and battery.

Are all ground connections clean and tight?

Yes	No
REPLACE generator rear assembly.	CLEAN or REPAIR grounds as required.

PINPOINT TEST R: INDICATOR LAMP FLICKERS/INTERMITTENT

R1 CHECK FOR LOOSE CONNECTIONS

Check the following for corrosion or loose connections:

voltage regulator connector
generator B+ wire
megafuse
underhood fuse box
battery ground cables

Are all connections clean and tight?

Yes	No
GO to R2.	CLEAN or REPAIR connections as required.

R2 CHECK FOR LOOSE A CIRCUIT FUSE

Start engine.
Check the generator fuse in the underhood fuse box for a loose connection by wiggling the fuse with the engine running.

Does indicator lamp flicker?

Yes	No
REPAIR loose fuse connection.	REPLACE generator rear assembly.

PINPOINT TEST S: GENERATOR NOISY

S1 CHECK FOR ACCESSORY DRIVE NOISE

Using Rotunda Belt Tension Gauge 014-R1056 or equivalent, check the drive belt for damage or improper tension. Refer to Section 03-05.
Check all accessory mounting brackets for loose bolts or misalignment.
Check for a bent pulley.

Is accessory drive OK?

Yes	No
GO to S2.	SERVICE accessory drive as required.

S2 SUBSTITUTE KNOWN GOOD GENERATOR

Remove generator and replace with a known good generator.

Is noise present with known good part?

Yes	No
Generator is OK. INSTALL original part. CHECK other accessories to find the cause of the noise.	REPLACE generator front assembly.

PINPOINT TEST T: RADIO INTERFERENCE

T1 VERIFY RADIO INTERFERENCE

Start engine.
Tune radio to a station where interference is heard.
Stop engine.
Remove voltage regulator connector and B+ wire.
Start engine.

Is interference present with connectors removed?

Yes	No
Generator is OK. REFER to Section 15-00 to find the cause of the radio interference.	GO to T2.

T2 SUBSTITUTE KNOWN GOOD GENERATOR

Remove generator and replace with a known good generator.

Is interference present with known good part?

Yes	No
Generator is OK. REFER to Section 15-00 to find the cause of the radio interference.	REPLACE generator rear assembly.