Ford F150 Pickup. Instruction - part 688

TEST C: SYSTEM OVERCHARGES (GREATER THAN 15.5 VOLTS)

1. Check For Voltage Drop In "A" Circuit (Orange/Light Blue Wire) 

 
Disconnect generator 3-pin harness connector. Turn ignition on. Measure voltage between generator 
terminal "A" (Orange/Light Blue) and positive battery terminal. If voltage is less than .5 volt, go to next 
step. If voltage is .5 volt or more, repair high resistance in circuit between generator and battery. 

2. Check Generator And Battery Ground Connections 

 
Turn ignition off. Inspect generator and regulator grounds (mounting surfaces and fasteners). Inspect 
battery ground. If problem exists, repair as necessary. On Lightning models, if all grounds are okay, 
replace generator. See GENERATOR under REMOVAL & INSTALLATION. On all other models, if 
all grounds are okay, replace voltage regulator. See VOLTAGE REGULATOR under REMOVAL & 
INSTALLATION.  

TEST D: WARNING INDICATOR IS ON WITH ENGINE RUNNING, SYSTEM IS CHARGING 

1. Check "I" Circuit (Light Green/Red Wire) For Short To Ground 

 
Disconnect generator 3-pin harness connector. Turn ignition on. Observe warning indicator. If warning 
indicator illuminates, repair short to ground in Light Green/Red wire between generator and instrument 
panel. On Lightning models, if warning indicator does not illuminate, replace generator. See 
GENERATOR under REMOVAL & INSTALLATION. On all other models, if warning indicator does 
not illuminate, go to next step. 

2. Inspect Generator "S" Terminal 

 
Turn ignition off. Connect generator harness connector. Check generator 1-pin harness connector for 
damage, corrosion and looseness (White/Black wire). If problem does not exist, go to next step. If 
problem exists, repair as necessary. 

3. Check Generator For Low Voltage 

Start engine and let idle. Using DVOM, backprobe and measure voltage between ground and generator 1-
pin harness connector terminal "S" (White/Black wire). See Fig. 1 . Increase engine speed to 2000 RPM. 
If voltage is 5 volts or more, replace voltage regulator. See VOLTAGE REGULATOR under 
REMOVAL & INSTALLATION. If voltage is less than 5 volts, replace generator. See GENERATOR 
under REMOVAL & INSTALLATION.  

TEST E: WARNING INDICATOR IS OFF WITH IGNITION ON 

1. Check The Charging System Warning Indicator Lamp 

 
Turn ignition off. Disconnect generator 3-pin harness connector. Connect a fused (15-amp) jumper wire 

NOTE:

There are 2 terminals "S" on generator. Ensure voltage measurement is 
made at 1-pin harness connector and not at 3-pin harness connector.

 

2003 Ford Pickup F150 

2003 STARTING & CHARGING SYSTEMS Generators & Regulators - F150 Pickup

  

between generator harness connector terminal "I" (Light Green/Red wire) and ground. See Fig. 2 . On 
Lightning models, if indicator warning light illuminates, replace generator. See GENERATOR under 
REMOVAL & INSTALLATION. On all other models, if indicator warning light illuminates, replace 
voltage regulator. See VOLTAGE REGULATOR under REMOVAL & INSTALLATION. On all 
models, if warning indicator does not illuminate, repair warning indicator as necessary. See appropriate 
ANALOG INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.  

TEST F: WARNING INDICATOR FLICKERS OR OPERATES INTERMITTENTLY 

1. Check For Loose Connections 

 
Inspect all generator, power distribution and battery connections for looseness, corrosion, and loose or 
bent terminals. If all connections are okay, go to next step. If a problem exists, repair as necessary. 

2. Check Fuse Connections 

 
Start engine and let idle. Inspect battery junction box fuse No. 11 (20-amp) for looseness. Inspect central 
junction box fuse No. 30 (30-amp) for looseness. Wiggle fuse connections and note warning indicator. If 
warning indicator does not flicker, go to next step. If warning indicator flickers, repair loose fuse 
connections as necessary. 

3. Check "A" Circuit (Orange/Light Blue) Connections 

 
Turn ignition off. Using a fused (15-amp) jumper wire connected to positive battery terminal, backprobe 
generator harness connector terminal No. "A" (Orange/Light Blue wire). See Fig. 2 . Start engine and let 
idle. Observe warning indicator. On Lightning models, if warning indicator flickers, replace generator. 
See GENERATOR under REMOVAL & INSTALLATION. On all other models, if warning indicator 
flickers, go to next step. On all models, if warning indicator does not flicker, repair loose connection(s) 
between generator and battery. See WIRING DIAGRAMS . 

4. Inspect Generator "S" Terminal 

 
Turn ignition off. Check generator 1-pin harness connector for damage, corrosion and looseness 
(White/Black wire). If problem does not exist, go to next step. If problem exists, repair as necessary. 

5. Check Generator Brushes 

 
Turn ignition off. Remove generator from vehicle. Measure resistance between voltage regulator "F" 
terminal screw on back of generator and generator 3-pin connector terminal "A" (component side). See 
Fig. 1 and Fig. 3 . If resistance is 5 ohms or more, go to next step. If resistance is less than 5 ohms, 
replace generator. See GENERATOR under REMOVAL & INSTALLATION. 

6. Check For A Grounded Slip Ring 

 
Remove voltage regulator and brush holder. Measure resistance between generator housing and each 
generator slip ring. See Fig. 4 . If resistance is 10 k/ohms or more between both slip rings and housing, 
replace voltage regulator. If resistance is less than 10 k/ohms between either slip ring and housing, 

 

2003 Ford Pickup F150 

2003 STARTING & CHARGING SYSTEMS Generators & Regulators - F150 Pickup

  

replace generator. See GENERATOR under REMOVAL & INSTALLATION. 

Fig. 4: Checking For Grounded Generator Slip Ring (Except Lightning) 
Courtesy of FORD MOTOR CO. 

TEST G: GENERATOR NOISY 

1. Check For Accessory Drive Noise 

 
Turn ignition off. 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. 

2. Check Generator Mounting 

 
Check generator installation. Ensure all fasteners are tight. If problem does not exist, go to next step. If 
problem exists, repair as necessary. 

3. Check Generator For Electrical Noise 

 
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. See GENERATOR under REMOVAL & INSTALLATION. 

 

2003 Ford Pickup F150 

2003 STARTING & CHARGING SYSTEMS Generators & Regulators - F150 Pickup

  

4. Check Generator For Mechanical Noise 

 
Turn ignition off. 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. See GENERATOR under REMOVAL & INSTALLATION. If generator is not source 
of noise, isolate noise and repair as necessary.  

TEST H: RADIO INTERFERENCE 

1. Verify Generator Is Source Of Radio Interference 

 
Start engine and let idle. Tune radio to station where interference is present. Turn ignition off. 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. See GENERATOR under REMOVAL & 
INSTALLATION.  

REMOVAL & INSTALLATION 

GENERATOR 

Removal & Installation (4.2L) 

Disconnect negative battery cable. Remove drive belt from generator pulley. Disconnect generator electrical 
connectors. Remove 3 mounting bolts and generator from vehicle. To install, reverse removal procedure. 
Tighten fasteners to specification. See TORQUE SPECIFICATIONS . 

Removal & Installation (4.6L & 5.4L 2V) 

Disconnect negative battery cable. Disengage drive belt from generator pulley. Remove 3 mounting bracket 
bolts. Remove generator mounting bolts and generator from vehicle. Disconnect generator electrical connectors. 
To install, reverse removal procedure. Tighten fasteners to specification. See TORQUE SPECIFICATIONS . 

Removal & Installation (Lightning) 

Disconnect negative battery cable. Remove retaining bolt securing degas bottle and position aside. Remove 
supercharger drive belt. Remove drive belt tensioner support bracket and drive belt from generator pulley. 
Loosen lower generator brackets and remove upper generator bracket bolts. Disconnect generator electrical 
connector from generator bracket. Remove right side generator lower mounting bolt. Remove engine bracket 
bolt and 2 generator bracket bolts. Rotate generator to access voltage regulator electrical connector. Disconnect 
electrical connectors and remove generator from vehicle. To install, reverse removal procedure. Tighten 

CAUTION: When battery is disconnected, vehicle computer and memory systems 

may lose memory data. Driveability problems may exist until computer 
systems have completed a relearn cycle. See COMPUTER RELEARN 
PROCEDURES - FORD article in GENERAL INFORMATION before 
disconnecting battery.

 

2003 Ford Pickup F150 

2003 STARTING & CHARGING SYSTEMS Generators & Regulators - F150 Pickup