Alternator & Regulator Buick Electra Estate Wagon

DESCRIPTION

Delco-Remy Delcotron alternators with integral regulators are used on American Motors Eagle and all General Motors vehicles. Delcotron alternators are available with different idle outputs and rated amp outputs of 37-100 amps. See Specification Chart at end of article.

Cutaway of Delcotron 10 SI Alternator w/ Integral Regulator. Scheme 1

All models feature a solid state regulator mounted inside the alternator. The construction and operation of all models is basically the same. Delcotron alternators consist primarily of 2 end frame assemblies, rotor, stator, brushes, slip rings and diodes. The rotor is supported in the drive end frame by ball bearings and in the slip ring end frame by roller bearings. The bearings are sealed and do not require periodic lubrication.

OPERATION

Two brushes carry current through the slip rings to the field coil mounted on the rotor. The stator windings are assembled on the inside of a laminated core that forms part of the alternator frame. A rectifier bridge connected to the stator windings contains 6 diodes (3 positive and 3 negative) molded into an assembly. The rectifier bridge changes stator A.C. voltage into D.C. voltage, which appears at the output "BAT" terminal.

The blocking action of the diodes prevents battery discharge back through the alternator. Because of this blocking action, need for a cutout relay is eliminated. The alternator field current is supplied through a diode trio, which is also connected to the stator windings. A capacitor is mounted in the end frame to protect the rectifier bridge and diodes from high voltage and to suppress radio noise.

ADJUSTMENTS

No periodic adjustment or maintenance is required on the alternator assembly. The regulator voltage is nonadjustable.

TROUBLE SHOOTING

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

TESTING (ON-VEHICLE)

Note. Before making electrical checks, visually inspect all terminals for clean and tight connections. Check alternator mounting bolt torque and drive belt tension. DO NOT ground the No. 2 lead wire. The battery must be in good condition to test the charging system.

Scheme 2

Scheme 3

Scheme 4

1. With ignition switch in "ON" position, connect a voltmeter from alternator "BAT" terminal to ground. (Scheme 2) Next, connect a voltmeter from No. 1 terminal to ground and then from No. 2 terminal to ground. A zero reading indicates an open between voltmeter connection and battery. (Scheme 2): Identification of Delcotron Terminal Locations 10 SI alternator is shown. NOTE: Alternators have a built-in feature, that avoids overcharging or accessory damage by preventing alternator from turning on if there is an open in wiring harness connected to No. 2 alternator terminal.
2. Opens in wiring harness connected between No. 2 terminal and battery may be between terminals, at crimp between harness wire and terminal, or in wire. If test results are satisfactory, proceed to step 3.
3. Disconnect battery ground cable. Connect an ammeter in series between "BAT" terminal of alternator and disconnected "BAT" lead. (Scheme 3) Reconnect battery ground cable and turn all accessories on. (Scheme 3): Alternator Connections for Bench Testing & On-Vehicle Check of Undercharged Battery
4. Connect a carbon pile across battery. Operate engine at a speed of 2000 RPM and adjust carbon pile as necessary to obtain maximum current output.
5. If ampere output is within 10 amps of rated output stamped on alternator case, alternator is good. If output is not within 10 amps of rated output, ground field winding tab by inserting a screwdriver into end frame test hole. (Scheme 4) (Scheme 4): View of Field Ground Tab Accessible Through Hole in End Frame CAUTION: Tab is within 3/4" of casting surface. DO NOT force screwdriver deeper than 1" into end frame.
6. Operate engine at a speed of 2000 RPM and adjust carbon pile as required to obtain maximum current output. If output is now within 10 amps, check field windings, diode trio, and voltage regulator. If output is not within 10 amps of rated output, check field windings, diode trio, rectifier bridge, and stator.

Note. If test hole is not accessible, disassemble alternator and test components.

OVERCHARGED BATTERY

If an overcharged condition exists, shown by excessive overflow of electrolite from battery, disassemble alternator and test field coils, rotor, and regulator.

Note. An overheated battery will be overcharged even though charging circuit defects are not present.

ALTERNATOR DIAGNOSTIC TESTER

Note. The Alternator Diagnostic Tester (J-26290) is designed as a quick check of alternator system, it will indicate about 98% of charging system faults.

Scheme 5

1. With engine, lights, and accessories turned off, connect Alternator Diagnostic Tester (J-26290) to alternator. (Scheme 5) If tester light flashes, go to step 3. If tester light stays on, tester is at fault and should be replaced. If tester light is off, pull tester plug from alternator. (Scheme 5): Alternator Diagnostic Tester Connections
2. If tester plug is pulled from alternator and tester light flashes, remove alternator and replace rectifier bridge. If tester light stays off, check for a defective wire of No. 2 terminal connector of wiring harness or check for a faulty tester.
3. With engine operating at fast idle speed (lights and accessories off), check condition of tester light. If tester light is off, charging system is good. If tester light is on, remove alternator and check diode trio, rectifier bridge, and stator. If tester light is flashing, remove alternator and check voltage regulator, rotor field coil, brushes, and slip rings.

VOLTAGE REGULATOR

1. Connect a fast charger and voltmeter to battery. (Scheme 6) Turn ignition switch on and slowly increase charging rate on fast charger. As voltage is increased, vehicle generator light will dim at voltage regulator setting.
2. Voltage regulator setting should be a minimum of 13.5 volts and a maximum of 16 volts. If voltmeter, vehicle generator light, or test light do not operate as described, replace voltage regulator.

On-Vehicle Voltage Regulator Test Observe battery polarity. Scheme 6

Note. The voltage regulator test works providing rotor field windings are good even though rectifier bridge or diode trio may be bad.

Scheme 7

1. Using an ohmmeter, check rotor windings for grounds, by setting it on x1000 scale. (Scheme 7) Connect one ohmmeter lead to rotor shaft and other lead to each slip ring. Resistance should be very high (infinity). If resistance is not infinity, replace rotor assembly. (Scheme 7): Bench Testing Rotor for Grounds and Opens
2. Set ohmmeter on x1 scale and test rotor for opens. Connect an ohmmeter lead to each slip ring (Scheme 7) The resistance reading should be 2.4-3.5 ohms. If resistance is not as specified, replace rotor assembly.

STATOR GROUNDS

To check stator for grounds, set an ohmmeter on x1000 scale. Connect one ohmmeter lead to stator frame and other lead to each stator lead. (Scheme 8) The resistance reading should be infinity. If resistance is low, stator is grounded and must be replaced.

Bench Testing Stator for Grounds Also test for opens on 10 SI and 12 SI alternators. Scheme 8

STATOR OPENS

Note. The delta windings of 15 SI, 17 SI, and 27 SI series alternators cannot be checked for open circuits. However, if all other electrical checks are normal and generator fails to supply rated output, but will supply at least 10 amps, windings are probably defective.

To check for open conditions of 10 SI and 12 SI stators, use an ohmmeter set on x1000 scale. Attach ohmmeter leads to any two stator leads. Check each combination of stator leads in succession. (Scheme 8) If any of ohmmeter readings are high (infinity), a winding is open. Replace stator assembly.

Scheme 9

1. Remove diode trio from end frame assembly. Connect one ohmmeter lead to brush connector and other lead to one of 3 stator lead connectors. Then reverse ohmmeter probes. (Scheme 9) A good diode will give one high and one low reading. If both readings are same, replace diode trio. (Scheme 9): Bench Testing Typical Diode Trio
2. Repeat test, touching leads in turn from single connector to each of 3 stator lead connectors. If any reading is zero, a short is indicated. Replace diode trio.

Note. Before replacing diode trio, check rectifier bridge.

RECTIFIER BRIDGE

Scheme 10

1. Connect one ohmmeter lead to grounded heat sink. Connect other ohmmeter lead firmly against flat metal portion of terminal (not threaded stud). (Scheme 10) Next, reverse leads to same heat sink and terminal. If both readings are same, replace rectifier bridge. (Scheme 10): Bench Testing Rectifier Bridge and Identification of End Frame Components
2. A good rectifier bridge will give one high and one low reading. Repeat this same test between grounded heat sink and other 2 flat metal connectors. Next, repeat same test between insulated heat sink and each of its 3 flat metal connectors.
3. Check other bridge rectifiers in same manner. DO NOT replace rectifier bridge or diode trio unless one pair of readings is same.

Bench Test

1. Remove voltage regulator from rectifier end shield. Connect a 12-volt battery, voltmeter, fast charger, and test light to voltage regulator. (Scheme 11) The test light should be on.
2. Turn fast charger on and increase charge rate. When charge rate reaches 13.5-16 volts, test light will turn off. If test light does not turn off, replace voltage regulator.

Note. Due to temperature differences, voltage regulator's operating specifications may vary.

Test Equipment Hookup for Voltage Regulator Check Observe battery polarity. Scheme 11

Scheme 12

1. Scribe alignment mark on both end frames for reassembly reference. Remove 4 through bolts and separate drive end frame and rotor from rectifier end frame and stator. (Scheme 12) Remove and clean brushes to prevent grease from soaking into brushes. (Scheme 12): Exploded View of 10 SI Alternator
2. Remove brush springs and place pressure sensitive tape (not friction tape) over rectifier end bearing and bearing shaft on rotor. Remove 3 nuts holding stator leads to rectifier bridge and remove stator.
3. Remove 1 screw with plastic insulator, holding diode trio to brush holder. Remove diode trio. Remove screws securing regulator and brush holder. Remove indicator lamp resistor, brush holder, and regulator.
4. Remove rectifier bridge by removing screw with washer, screw at capacitor lead, and nut/washer from "BAT" terminal stud. Remove insulator and "BAT" terminal stud. Remove screw securing capacitor to end of frame.
5. To remove rotor from drive end frame, install rotor in vise, but only tight enough to remove shaft nut, washer, pulley, fan, and collar. Separate end frame from rotor.

Bearing Replacement

1. To remove bearing in drive frame end, detach retainer plate screws and press bearing from frame. If bearing is in good condition, it can be reused. To install bearing, press it in with a tube or collar that just fits over outer race. Install a new retainer plate if felt seal is hardened or excessively worn. NOTE: All alternators use sealed bearings and no lubrication is needed.
2. Replace bearing in rectifier end frame if bearing is damaged. DO NOT attempt to relubricate or reuse bearing. Press bearing from outside of housing toward inside, using a tube or collar just fitting inside of end frame housing.
3. To install a new bearing, place a flat plate over bearing and press it in from outside until bearing is flush with outside of end frame. Support underside of end frame with a hollow cylinder while pressing in bearing.
4. Always install a new seal whenever a bearing is replaced. Press seal in with lip of seal toward rotor, away from bearing. Coat seal lip lightly with oil to aid in later assembly.

Drive End Frame Bearing Assembly. Scheme 13

INSPECTION

Wash all metal parts except bearings, stator, and rotor. Inspect rotor slip rings and clean with 400 grit or finer polishing cloth. Hold cloth against slip rings and spin rotor to clean evenly and avoid flat spots. The slip rings may be lathe turned to a .002" (.05 mm) indicator reading. Slip rings are not replaceable. Excessive damage will require rotor replacement. Inspect brushes for wear. Clean with acetone if necessary, and replace if excessively worn.

REASSEMBLY

1. Position "BAT" terminal stud in end frame with molded plastic insulator outside and fiber insulator inside. Place rectifier bridge in end frame and secure it with a nut and washer at one end and a screw and washer at other. Install capacitor to end frame and heat sink.
2. Position regulator in rectifier end frame. Install indicator lamp resistor and brush holder over regulator and install screws securing regulator. Place diode trio on rectifier bridge and attach it to regulator with an insulated screw.
3. Place stator on end frame, with leads over rectifier bridge studs. Secure with nuts. Install brush springs and brushes in holder. Insert a straight wire or pin through hole in end frame and holes in bottom of brush holder. NOTE: This will hold brushes in place until rotor is assembled into frame.
4. Place rotor in a vise with drive end up. DO NOT overtighten vise. Install end frame, fan, pulley, and washer over rotor shaft and secure with a nut. Tighten nut to 40-60 ft. lbs. (54-81 N.m). Install rotor to rectifier end frame, aligning scribe marks. Remove wire holding brushes. Install 4 through bolts through end frames and tighten.

SPECIFICATIONS

DELCO-REMY "DELCOTRON" ALTERNATOR TEST SPECIFICATIONS

See also:
• TROUBLE SHOOTING - BASIC PROCEDURES