Bronco II 4WD V6-171 2.8L (1985)
2.
Increase the engine speed to 2000 rpm. The voltmeter should indicate a minimum of 0.5 volt above the base voltage. If not, perform the under
voltage test described below.
If the above tests indicate proper voltage readings, the charging system is operating normally. Use test lamp and check for battery drain.
Over Voltage Tests
If the voltmeter indicates more than 2.0 volts above base battery voltage:
1.
With ignition ON and engine OFF, connect the voltmeter negative lead to the alternator rear housing. Contact the voltmeter positive lead first to
the alternator output connection at the starter solenoid and then to the regulator A screw head. If the voltage difference between the two locations
is greater than 0.5 volt, service the A wiring circuit to eliminate the high resistance condition indicated by the excessive voltage drop.
2.
If over voltage condition still exists, check for loose regulator to alternator grounding screws. Tighten loose regulator grounding screws to 1.7-2.8
N-m (15-26 in.lbs.).
3.
If over voltage condition still exists, connect the voltmeter negative lead to the alternator rear housing. With ignition OFF, contact the voltmeter
positive lead first to the regulator A screw head and then to the regulator F screw head. Different voltage readings at the two screw heads indicates
a defective regulator, grounded brush lead or a grounded rotor coil. Service the entire integral alternator/regulator assembly.
4.
If the same voltage reading (battery voltage) is obtained at both screw heads in Step 3 and there is no high resistance in the ground or A+ circuits,
then the regulator calibration is high. Replace the regulator.
Under Voltage Tests
If the voltmeter does not indicate more than 0.5 volt above the base voltage:
1.
Disconnect wiring plug from regulator and connect an ohmmeter between the regulator A and F terminal screws. The meter should indicate more
than 2.2 ohms. If less than 2.2 ohms is indicated, service the integral alternator/regulator unit for a failed regulator and check the alternator for a
shorted rotor or field circuit. Perform the Load Test after servicing.
CAUTION: DO NOT REPLACE THE REGULATOR BEFORE A SHORTED ROTOR COIL OR FIELD CIRCUIT HAS BEEN SERVICED.
REGULATOR DAMAGE COULD RESULT.
2.
If the above ohmmeter reading is greater than 2.2 ohms, reconnect the regulator wiring plug and connect the voltmeter ground lead to the
alternator rear housing. Contact the voltmeter positive lead to the regulator A terminal screw. The meter should indicate battery voltage. If there is
no voltage, service the A circuit. Perform Load Test after servicing.
3.
If the voltmeter indicates battery voltage, connect the voltmeter ground lead to the alternator rear housing. With the ignition switch OFF, contact
the voltmeter positive lead to the regulator F terminal screw. The meter should indicate battery voltage. If there is no voltage, service the integral
alternator/regulator unit for an open field circuit. Perform Load Test after servicing.
4.
If the voltmeter indicates battery voltage, connect the voltmeter negative lead to the alternator rear housing. Turn the ignition switch ON (engine
OFF) and contact the voltmeter positive lead to the regulator F terminal screw. The voltmeter should indicate 1.5 volts or less. If more than 1.5
volts is indicated, perform the I circuit tests and service the I circuit if needed. If the I circuit checks normal, replace the regulator and perform the
Load Test.
5.
If 1.5 volts or less is indicated, disconnect the alternator wiring plug and connect a set of 12 gauge jumper wires between the alternator B+
terminal blades and the mating wiring connector terminals. Perform the Load Test, but connect the voltmeter positive lead to one of the B+ jumper
wire terminals. If the voltage rises more than 0.5 volts above base voltage, service the alternator to starter relay wiring. Repeat the Load Test
measuring the voltage at the battery cable clamps after servicing.
6.
If the voltage does not rise more than 0.5 volt above base voltage, connect a jumper wire from the alternator rear housing to the regulator F
terminal. Repeat the Load Test with the voltmeter positive lead connected to one of the B+ jumper wire terminals. If the voltage rises more than
0.5 volt, replace the regulator.
7.
If the voltage does not rise more than 0.5 volt, service the alternator.
Regulator I Circuit Tests
1.
Disconnect the wiring plug from the regulator. Connect the voltmeter negative lead to the battery ground terminal and the positive lead to the
wiring plug I terminal. No voltage should be indicated with the ignition switch OFF. If voltage is indicated, service the I lead from the ignition
switch to identify and eliminate the voltage source.
2.
Turn the ignition switch to ON. The voltmeter should indicate battery voltage at the wiring plug I terminal. If there is no voltage reading, service
the I lead from the ignition switch to the regulator for an open or grounded circuit.
