Alternator - Models W/external Regulator Ford Bronco II I

IDENTIFICATION & SPECIFICATIONS

Alternator is color-ink stamped with "Motorcraft" trademark. Color stamp is coded for rated amperage output. Rated amperage is

ALTERNATOR OUTPUT

ALTERNATOR SPECIFICATIONS

Scheme 1

Scheme 2

DESCRIPTION

Light truck alternators are available with rear or side mounted terminals. (Scheme 1)and (Scheme 2). Rated outputs range from 40 to 100 amps depending upon model used. Some models are equipped with indicator lights while others use ammeters.

Current is supplied to the system from rotating field of alternator through 2 brushes contacting 2 slip rings. Alternating current is produced and then is rectified to direct current by the use of diodes. Charging systems are equipped with a fusible link between starter relay and alternator "BAT" terminal.

ALTERNATOR REGULATOR

An electronic regulator is used on all charging systems. Regulator is factory calibrated and cannot be adjusted.

TROUBLE SHOOTING

Note. See TROUBLE SHOOTING - BASIC PROCEDURES article in the GENERAL TROUBLE SHOOTING section.

TESTING PRECAUTIONS

When testing or servicing alternator or regulator, use caution to avoid damaging components.

Battery

Do not reverse battery connections. Negative terminal must be connected to ground. When charging battery, remove ground cable before connecting charger. If booster battery is used to start engine, negative cable of booster must be connected to vehicle frame. Disconnect negative booster cable first.

Do not ground field circuit between alternator and regulator, or operate alternator on an open circuit with field winding energized. Do not ground output terminal or attempt to polarize alternator.

Turn ignition switch to "OFF" position when working on regulator. This is done to ensure that power wire is not grounded.

CHARGING SYSTEM TESTING

Note. Ensure that battery is fully charged and battery connections are clean and secure. On non-maintenance free batteries specific gravity must be at least 1.200 prior to testing. Check that alternator drive belt is adjusted to proper tension.

1. Ensure that all accessories are turned off. Use voltmeter to measure battery voltage. Attach tachometer and start engine. Operate at 1500 RPM with no electrical load. Voltmeter reading should increase but should be no more than 2.5 volts above battery voltage. Reading should be taken when voltmeter needle stabilizes.
2. With engine operating, turn heater or A/C blower motor to "HIGH" position. Turn on headlights to high beam. Increase engine speed to 2000 RPM. Voltmeter should indicate a minimum of .5 volt above battery voltage.

TEST RESULTS

1. If voltmeter reading indicates more than 2.5 volts above battery voltage, stop engine, and connect jumper wire between regulator base and alternator frame. Perform voltage test again.
2. If voltage is 2.5 volts or less, check ground connections on alternator and regulator. Repeat test once repair is made.
3. If over-voltage condition still exists, disconnect regulator wiring plug and repeat steps 1) and 2) of CHARGING SYSTEM TESTING. If condition is corrected, replace regulator and repeat test.
4. If over-voltage still exists with regulator disconnected, repair wiring harness between alternator and regulator circuits "A" and "F". Connect regulator and repeat tests once repair is made.

"S" Circuit With Ammeter

1. Disconnect regulator wiring plug. Connect positive voltmeter lead to regulator wiring plug "S" terminal position. Connect voltmeter negative lead to secure ground. Turn ignition switch to "ON" position.
2. Voltmeter should indicate battery voltage. Check the "S" wire lead from ignition switch for open circuit if no voltage exists. Repair wiring and retest system.

Scheme 3

1. Disconnect regulator wiring plug. Install jumper wire between "A" and "F" terminals. Start engine and allow to idle. Connect voltmeter negative lead to ground. Connect voltmeter positive lead to "S" and then to "I" terminals of regulator wiring plug. (Scheme 3)
2. Voltage reading of "S" circuit should be 1/2 that of "I" circuit voltage. Replace regulator if voltage readings are correct. Remove jumper wire from regulator wiring plug. Connect plug to regulator and repeat CHARGING SYSTEM TESTING.
3. If no voltage exists, check for damaged wiring. Connect voltmeter positive lead to positive battery post. Remove jumper wire from regulator wiring plug. Connect plug to regulator and repeat CHARGING SYSTEM TESTING.

UNDER VOLTAGE TESTS

1. Disconnect regulator wiring plug. Install ohmmeter lead on negative battery terminal. Install remaining lead on the "F" terminal of the plug. (Scheme 3) Note ohmmeter reading.
2. Reading should exceed 2.4 ohms. If reading is not within specification, check for grounded field circuit in wiring harness or alternator.
3. If ohmmeter reading is less than 2.4 ohms, connect jumper wire from the "A" to "F" terminal. Repeat charging system test. See «CHARGING SYSTEM TESTING»(/ford/bronco-ii/i-1984-1990/remont/charging-system/#alternator-models-wexternal-regulator__charging-system-testing). If voltage exceeds.5 volt, voltage regulator wiring must be tested. See "S" and "I" CIRCUIT under «REGULATOR CIRCUIT TESTS»(/ford/bronco-ii/i-1984-1990/remont/charging-system/#alternator-models-wexternal-regulator).
4. Perform following step if low voltage is obtained with jumper installed. Remove jumper wire. Do not plug wiring connector into regulator. Disconnect "FLD" terminal on rear of alternator.
5. Connect jumper wire between alternator "BAT" and "FLD" terminals. Repeat charging system test. See «CHARGING SYSTEM TESTING»(/ford/bronco-ii/i-1984-1990/remont/charging-system/#alternator-models-wexternal-regulator__charging-system-testing). If voltage reading now indicates a.5 volt reading, check wiring or regulator.
6. Perform following step if low voltage is obtained. Position voltmeter positive lead on alternator "BAT" terminal. If battery voltage is obtained, replace alternator. If no voltage is shown, repair the alternator-to-starter relay wire or fusible link.

FIELD OPEN OR SHORT CIRCUIT TEST

1. Perform test before alternator disassembly. Adjust ohmmeter to the x1 scale. Place ohmmeter probe on alternator "FLD" terminal. Place remaining ohmmeter probe on alternator "GRD" terminal.
2. Rotate alternator pulley and note reading. Ohmmeter reading should be between 2.4 and 100 ohms. Reading should fluctuate while pulley is spinning.
3. Infinite reading indicates open brush lead, damaged brushes or bad rotor assembly. Check for grounded brush assembly, grounded field terminal, or defective rotor if ohmmeter reading is less than 2.4 ohms.

RECTIFIER SHORT OR GROUNDED & STATOR GROUNDED TEST

1. Adjust ohmmeter to the x1 scale. Place ohmmeter probe on alternator "BAT" terminal. Place remaining probe on "STA" terminal. Note reading in this procedure. Reverse probes and note reading.
2. Perform same test procedure using "STA" and "GRD" terminals. Reading in both directions indicates defective negative diode, grounded stator, stator terminal, grounded positive diode plate or "BAT" terminal.
3. There should be no reading in one direction and a low reading in the other position. Low reading of approximately 6 ohms should be obtained in one direction.
4. Reading in both directions indicates defective positive diode, grounded diode plate or "BAT" terminal.
5. Infinite reading with probes in one direction and no reading or excessive resistance in other, indicates bad connection on stator terminal and stator bolt head.

STATOR COIL GROUNDED TEST

1. Adjust ohmmeter to the x1000 scale. Place ohmmeter probes on one of stator leads and to stator laminated core. Ohmmeter reading should show no reading.
2. Stator winding is shorted if reading is obtained. Replace stator coil if shorted. Repeat test procedure for each stator lead.

STATOR COIL OPEN TEST

1. Adjust ohmmeter to the x1 scale. With stator coil removed from rectifier, place ohmmeter probes on each stator lead. Ohmmeter reading should be obtained.
2. Stator winding is open if reading is not obtained. Replace stator coil if open is found. Repeat test procedure on remaining stator leads.

DIODE TEST

1. Adjust ohmmeter to the x1 scale. Remove rectifier assembly from alternator. Place ohmmeter probe on terminal bolt. Touch remaining probe on each of the 3 stator lead terminals. Note ohmmeter reading. Reverse probes and repeat test.
2. Diodes should show a reading of approximately 6 ohms in one direction, and infinite readings with probes reversed. Repeat test for remaining set of diodes using the other terminal screw. Replace rectifier assembly if readings are not within specification.

ROTOR OPEN OR SHORT CIRCUIT TEST

1. Adjust ohmmeter to the x1 scale. With rotor removed, place ohmmeter probes on a rotor slip ring. Reading should be 2.0-3.5 ohms. Reading exceeding specification indicates damaged slip ring solder connection or broken wire.
2. Reading lower than specification indicates shorted wire or slip ring. Replace rotor if damaged. Place one ohmmeter probe on slip ring and remaining probe on rotor shaft.
3. Meter reading should not be obtained. If reading is obtained, rotor is shorted to shaft. Check that slip ring terminals or solder is not touching rotor shaft. This will cause a shorted condition. Replace rotor if shorted.

Scheme 4

1. Mark housings and stator with scribe for reassembly. Remove through bolts and separate front housing with rotor from stator and rear housing. Remove all nuts and insulators from rear housing. Remove rear housing from stator and rectifier assembly. (Scheme 5)
2. Clamp front housing in soft-jawed vise. Remove drive pulley nut. Remove lock washer, pulley, fan and spacer from rotor shaft. Remove rotor from front housing. Remove front bearing spacer. Do not remove rotor stop ring unless damaged.
3. Remove front bearing retainer. If bearing has lost lubricant or is damaged, remove bearing. Support front housing close to bearing boss. Press out old bearing.
4. Remove brush holder, brushes, springs, insulator and terminal. Press bearing from rear housing if bearing replacement is required. Support housing on inner boss while removing bearing.
5. If rectifier assembly is being replaced, unsolder stator leads from rectifier terminals. Use 100-watt soldering iron and use care not to apply direct heat to rectifier. Separate stator from rectifier assembly.
6. Different types of rectifier assemblies are used. Rectifier assembly may have circuit board spaced away from diode plates. The external diodes are exposed. The other type is a rectifier assembly with internal diodes. (Scheme 4)
7. If alternator rectifier has exposed diode board, remove stator lead screws from rectifier by rotating screw 1/4 turn clockwise to unlock. Remove retaining screws.
8. On rectifier with internal diodes, stator lead screw must be pushed from rectifier. Do not turn stator lead screw during removal. Rotation of stator lead screw will damage serrations used to retain terminal screw. Do not remove grounded screw.

Scheme 5

Cleaning & Inspection

1. Rotor, stator and bearing must not be cleaned with solvent. Clean these components with a clean cloth. Clean remaining components with clean solvent. Inspect bearings for signs of lubricant loss and signs of roughness.
2. Inspect rotor shaft bearing area for signs of bearing movement. Inspect all soldered connections on rotor and stator for looseness. Inspect rotor and stator for signs of burned insulation.
3. Inspect rotor slip rings for nicks or roughness. Rotor slip rings can be turned down to remove nicks or roughness. Rotor slip rings must not be turned smaller than specification. See «ALTERNATOR SPECIFICATIONS»(/ford/bronco-ii/i-1984-1990/remont/charging-system/#alternator-models-wexternal-regulator) table.
4. Check brush length. Replace brushes if worn less than .250" (6.35 mm). Replace all damaged components.

Note. Only high-temperature rectifier and bearings must be used when rebuilding 60-amp high-temperature alternator. Alternator failure will result if standard components are used.

Scheme 6

Scheme 7

1. Press bearing in front housing bearing boss. Apply pressure on bearing outer race only. Install bearing retainer and screws. Tighten to proper specification. See «TORQUE SPECIFICATIONS»(/ford/bronco-ii/i-1984-1990/remont/charging-system/#alternator-models-wexternal-regulator) table.
2. Install new rotor stop ring on rotor drive shaft (if removed). Use care not to deform rotor stop ring during installation. NOTE: Do not open ring with snap ring pliers, as permanent damage will result.
3. Position rotor stop on rotor shaft with recessed side against stop ring. Position front housing, fan spacer, fan, pulley and lock washer on rotor shaft. Install retaining nut and tighten to specification. See «TORQUE SPECIFICATIONS»(/ford/bronco-ii/i-1984-1990/remont/charging-system/#alternator-models-wexternal-regulator) table.
4. If rear housing bearing was removed, support housing on inner boss. Press new bearing in housing until it is even with outer end surface. Place brush springs, brushes, brush terminal and terminal insulator in holder.
5. Brushes may be held in position by inserting a small piece of stiff wire in brush holder. (Scheme 6)
6. Position brush holder assembly in rear housing and install mounting screws. Ground brush lead must be positioned under mounting screw. (Scheme 7)
7. Rectifier must be installed on stator. On external diode rectifiers, position stator lead and dished washer on rectifier. Install stator lead screw. Rotate screw 1/4 turn counterclockwise to lock in position.
8. On internal diode rectifier, place stator terminal insulator and stator lead on rectifier. Install terminal screw and press in position. Terminal screw should be installed enough to hold phase lead in place.
9. Ensure that all insulators are installed. Place stator lead on rectifier leads. Solder leads using rosin core solder. Use care not to apply direct heat to rectifier.
10. Position capacitor on rectifier terminals. Install "STA" and "BAT" terminal insulators on rectifier. Install stator and rectifier assembly in rear housing. Ensure all terminal insulators are seated in recesses.
11. Install "STA" (Black), "BAT" (Red), and "FLD" (Orange) insulators on terminal bolts. Install retaining nuts and tighten to specification. See «TORQUE SPECIFICATIONS»(/ford/bronco-ii/i-1984-1990/remont/charging-system/#alternator-models-wexternal-regulator) table.
12. Clean rear bearing surface of rotor shaft with clean cloth. Position rear housing and stator assembly over rotor. Align scribe marks made during disassembly.
13. Position machined portion of stator core in step area of both end housings. Install housing through bolts. Tighten to specification. See «TORQUE SPECIFICATIONS»(/ford/bronco-ii/i-1984-1990/remont/charging-system/#alternator-models-wexternal-regulator) table. Remove brush retaining wire.

Scheme 8

1. Mark housings and stator for reassembly. Remove through bolts. Separate front housing with rotor from rear housing and stator. Do not separate rear housing from stator. Remove drive pulley nut, lock washer, pulley, fan and spacer from rotor shaft. (Scheme 9)
2. Remove rotor from front housing. If bearing is dry or damaged, remove front bearing retaining screws. Support housing near bearing boss and press bearing from housing. Unsolder stator leads from rectifier assembly with 100-watt soldering iron. Use care not to apply direct heat to rectifier.
3. Remove stator from rear housing. Unsolder brush holder from rectifier. Remove capacitor lead from rectifier screw. Remove rectifier retaining screws from rear housing. Remove terminal nuts and insulators from outside of rear housing. Remove rectifier from rear housing.
4. Remove brush holder, brushes and 2 rectifier insulators from bosses in housing. Clean sealing compound from rear housing and brush holder. Remove capacitor from rear housing. If necessary to replace rear bearing, support rear housing near bearing boss and press bearing from inside of housing.

Scheme 9

1. Rotor, stator and bearing must not be cleaned with solvent. Clean these components with a clean cloth. Clean remaining components with clean solvent. Inspect bearings for signs of lubricant loss or roughness.
2. Inspect rotor shaft bearing area for signs of bearing movement. Inspect all soldered connections on rotor and stator for looseness. Inspect rotor and stator for signs of burned insulation.
3. Inspect rotor slip rings for nicks or roughness. Rotor slip rings can be turned down to remove nicks or roughness. Rotor slip rings must not be turned smaller than specification. See «ALTERNATOR SPECIFICATIONS»(/ford/bronco-ii/i-1984-1990/remont/charging-system/#alternator-models-wexternal-regulator) table.
4. Check brush length. Replace brushes if worn less than .250" (6.35 mm). Replace all damaged components.

Note. High-temperature rectifier and bearings must be used when rebuilding high-temperature alternator. Alternator failure will result if standard components are used.

Reassembly

1. Press bearing into front housing. Apply pressure on bearing outer race only. Install bearing retaining screws. Tighten to specification. See «TORQUE SPECIFICATIONS»(/ford/bronco-ii/i-1984-1990/remont/charging-system/#alternator-models-wexternal-regulator) table.
2. Install spacer on rotor shaft. Place rotor in front housing. Install fan, spacer, pulley, lock washer, and nut onto rotor shaft. Tighten pulley nut to specification. See «TORQUE SPECIFICATIONS»(/ford/bronco-ii/i-1984-1990/remont/charging-system/#alternator-models-wexternal-regulator) table.
3. Install rear bearing in housing. Install bearing until bearing is even with boss outer surface. Install brush terminal, brushes and springs on brush holder.
4. Insert a small piece of stiff wire in brush holder to retain brushes. (Scheme 8) Install brush holder to rear housing and install attaching screws. Ensure that small wire extends through rear housing so wire can be removed.
5. Push brush holder toward rotor shaft opening and tighten screws. Crack between brush holder and brush cavity in rear housing must be sealed using Sealer (D6AZ-19560-A). CAUTION: DO NOT use silicone base sealer for sealing brush cavity.
6. Install capacitor to rear housing. Install rectifier insulators on bosses on inside of rear housing. Install insulator on "BAT" terminal of rectifier. Position rectifier in rear housing. Install outside insulator on "BAT" terminal.
7. Install nuts on "BAT" and "GRD" terminals finger tight only. Install rectifier retaining screws. DO NOT tighten at this time. Tighten "BAT" and "GRD" terminals nuts to specification. See «TORQUE SPECIFICATIONS»(/ford/bronco-ii/i-1984-1990/remont/charging-system/#alternator-models-wexternal-regulator) table.
8. Tighten rectifier screws to specification. Secure capacitor lead to rectifier. Press brush holder lead on rectifier pin and solder leads.
9. Install stator in rear housing aligning scribe marks. Press 3 stator leads onto rectifier pins. Solder leads using care not to apply direct heat to rectifier.
10. Position rotor and front housing into stator and rear housing. Align scribe marks. Install through bolts and tighten. Rotate alternator to ensure free movement.
11. Remove brush retaining wire. Apply small amount of waterproof cement over hole to seal from moisture.

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

See also:
• TROUBLE SHOOTING - BASIC PROCEDURES
• CHARGING SYSTEM TESTING
• REGULATOR CIRCUIT TESTS