Alternator & Regulator Chevrolet Chevy Van G20

DESCRIPTION

Two types of alternators are used: 12/17SI series and CS130/144 series. The first series is designated SI (Systems Integral) because of the built-in regulator. The solid state regulator is enclosed in a solid mold. This unit, along with brush holder assembly, is attached to the slip ring end frame. Regulator voltage setting cannot be adjusted. All 12SI alternators have "Y" type stator windings, while all 17SI have delta type windings. A condenser, mounted in the end frame, protects the rectifier bridge and diode trio from high voltages and suppresses radio noise.

The CS130/144 (Charging System) alternators have a high amperage output. The 130 or 144 designation is the outside diameter of the stator laminations, measured in millimeters. This alternator series also has an integral regulator but does not have a diode trio. The delta wound stator, rectifier bridge, rotor with slip rings, and brushes are similar to other alternators.

Scheme 1

CS SERIES

Regulator voltage varies to compensate for temperature. Voltage is regulated by controlling rotor field current. The regulator switches rotor field current on and off at a fixed frequency of approximately 400 cycles per second.

The regulator has 4 terminals "P", "L", "I", and "S". (Scheme 1) The "L" terminal and/or the "I" terminal is used to turn on the regulator and allows field current to flow when the ignition switch is turned to START or RUN. The "L" terminal is connected through a charging indicator light or resistor. The "I" terminal is connected to the battery positive terminal either directly or through a resistor. These terminals are often used in parallel, and are connected to 2 different vehicle circuits. The "P" terminal is connected internally to the stator and may be wired to a tachometer or other device. The "S" terminal may be used to sense voltage at another vehicle location for voltage control. If "S" terminal is not used, alternator uses an internal sensor for voltage control.

SI SERIES

When ignition switch is turned to RUN or START, current from battery flows to ground through charging indicator light, No. 1 terminal and regulator, then back to battery, lighting charge indicator light.

When alternator is operating, DC voltage is applied to battery through the BAT terminal. (Scheme 1) Some of the current is routed through the diode into field coil, then through wire at the No. 1 terminal to charging indicator light. Light should go out since there is equal voltage on both sides of light. Vehicles with gauges use a voltmeter in this circuit.

TROUBLE SHOOTING

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

ON-VEHICLE TESTING

Note. Before making electrical checks, visually inspect all terminals for clean, tight connections. Check alternator mounting bolts and drive belt tension. Battery must be in good condition to test charging system.

Overcharged Or Undercharged Battery

1. If an overcharging condition is suspected, run engine at a moderate speed. Connect a voltmeter across battery terminals. If voltmeter indicates more than 16 volts, replace alternator.
2. If an undercharging condition is suspected, disconnect 4-wire connector from alternator. Turn ignition on with engine off. Connect a voltmeter between terminal "L" in wiring harness and ground. (Scheme 1) Record reading.
3. If terminal "I" is used, connect voltmeter between terminal "I" and ground. Record reading. If voltmeter reads battery voltage, circuits are okay. If voltmeter reads zero, this indicates an open circuit between terminal checked and battery. Repair as necessary.

Alternator Output Test

1. Connect an ammeter in circuit at BAT terminal of alternator. (Scheme 1) Turn on all available accessories. Connect a carbon pile across battery. Operate engine at 2000 RPM and adjust carbon pile as required to obtain maximum current output while maintaining 13 volts or more.
2. Ampere output must be within 15 amps of rated output. If output is not within 15 amps of rated output, replace alternator. See the «ALTERNATOR IDENTIFICATION & OUTPUT»(/chevrolet/chevy-van-g20/1985-1995/remont/charging-system/#alternator-regulator) at end of this article.

1. If an overcharging condition is suspected, attach a voltmeter across battery terminals. Run engine at a moderate speed with all accessories off. If voltmeter reads 15.5 volts or more, remove alternator for repair.
2. If an undercharging condition is suspected, turn ignition on. Connect a voltmeter from the alternator BAT terminal to ground. (Scheme 1) Voltmeter should read 12 volts. Connect voltmeter between No. 1 terminal and ground. Voltmeter should read one volt or more.
3. Connect voltmeter between No. 2 terminal and ground. Voltmeter should read 12 volts. A zero reading on any connection indicates an open between connection and battery. Opens may be at the crimp between harness wire and No. 2 terminal, or in wire.

1. Connect an ammeter in circuit at BAT terminal of alternator. (Scheme 1) Turn on all available accessories. Connect a carbon pile across battery. Operate engine at 2000 RPM and adjust carbon pile as required to obtain maximum current output.
2. Ampere output must be within 10 amps of rated output. See the «ALTERNATOR IDENTIFICATION & OUTPUT»(/chevrolet/chevy-van-g20/1985-1995/remont/charging-system/#alternator-regulator) at end of this article. If output is not within 10 amps of rated output, ground field winding by inserting a screwdriver into test hole. Repeat step 1). NOTE: Tab is within 3/4" of casting surface. DO NOT force tool into end frame beyond 1". If test hole is not accessible, proceed to «BENCH TESTING»(/chevrolet/chevy-van-g20/1985-1995/remont/charging-system/#alternator-regulator__bench-testing).
3. If output increases to within 10 amps of rated output with field grounded, regulator is defective. If output remains below 10 amps of rated output, check field winding, diode trio, rectifier bridge, and stator. See «BENCH TESTING»(/chevrolet/chevy-van-g20/1985-1995/remont/charging-system/#alternator-regulator__bench-testing) in this article.

BENCH TESTING

Note. There are no internal checks for CS130 series alternators.

Rotor Field Winding Test

1. To check for grounds, attach one ohmmeter lead to shaft and remaining ohmmeter lead to any slip ring. (Scheme 2) If reading is low (not infinity), replace rotor.
2. To test for open field, attach ohmmeter leads to each slip ring. (Scheme 2) Resistance should be low (not infinity). If reading is high (infinity), replace rotor.

Stator Inspection

Delco CS series alternators have delta stator windings and cannot be tested for grounded or open circuits with ohmmeter. A noticeable discoloration anywhere on the stator usually indicates stator failure.

Note. Some digital ohmmeters cannot be used to check the diodes in the rectifier bridge. Consult ohmmeter manufacturer to determine ohmmeter's capabilities.

Rectifier Bridge Test

1. Position ohmmeter with one lead touching Grounded Heat Sink and the other lead pressed firmly against flat metal on one of the 3 terminals or threaded studs. Observe reading and reverse test lead connections. (Scheme 5)
2. If both readings are the same, replace rectifier bridge. A good bridge will give a high and low reading. Repeat tests for remaining terminals. There should be 6 tests altogether (2 tests at each terminal).
3. Connect test leads to Insulated Heat Sink and one of the 3 terminals. (Scheme 5) Observe reading and reverse connections. Repeat tests for remaining terminals. There should be a total of 6 tests (2 at each terminals).
4. Testing is complete when all 12 tests have been made. If any of the terminals has same readings for both connections (leads reversed), replace rectifier bridge.

1. To check for grounds, attach one ohmmeter lead to shaft and remaining ohmmeter lead to any slip ring. (Scheme 2) If ohmmeter does not read infinity, replace rotor. Repeat test for remaining slip ring.
2. To test for open field, attach ohmmeter leads to each slip ring. (Scheme 2) Resistance should measure about 2.4-2.8 ohms on 12SI series, or 1.7-2.1 ohms on 17SI series. If resistance is not as specified, replace rotor.

Stator Test

1. To test 12SI series alternator for open, measure resistance between the stator leads by connecting ohmmeter leads to stator leads (in pair). (Scheme 3) If resistance is infinite, replace stator. NOTE: Delco 17SI alternator has delta stator windings and cannot be checked for open circuit.
2. On all models, connect one ohmmeter lead to any stator lead; connect remaining ohmmeter lead to stator frame. Ohmmeter reading should be infinity. (Scheme 3)

Diode Trio Test

1. Remove diode trio from end frame. Connect one ohmmeter lead to the single connector, and connect remaining lead to one of the 3 connectors. (Scheme 4) Note reading and reverse leads. If readings are the same, replace diode trio.
2. A good diode trio will give a high and low reading. Repeat tests for remaining connectors. Also, connect ohmmeter leads to the 3 connectors (in pair). If any reading is zero, replace diode trio.

1. Position ohmmeter with one lead touching Grounded Heat Sink and the other lead pressed firmly against flat metal on one of the 3 terminals or threaded studs. Observe reading and reverse test lead connections. (Scheme 5)
2. If both readings are the same, replace rectifier bridge. A good bridge will give a high and low reading. Test all terminals (6 tests).
3. Connect test leads to INSULATED heat sink and one of the 3 terminals. Observe reading and reverse connections. Repeat tests for remaining terminals. There should be a total of 6 tests (2 at each terminals).
4. Testing is complete when all 12 tests have been made. If readings at any of the terminals are same for both connections (leads reversed), replace the diode trio or rectifier bridge.

Scheme 2

Scheme 3

Scheme 4

Scheme 5

DISASSSEMBLY & REASSEMBLY

Note. Step by step overhaul procedures are not available from manufacturer. For overview of DISASSSEMBLY & REASSEMBLY procedures, see appropriate figure for exploded view of specific alternator model. Exploded view of model CS130 alternator is not available.

Scheme 6

Scheme 7

Scheme 8

INSPECTION

Wash all metal parts except bearings, stator and rotor. Inspect rotor slip rings. They may be cleaned with 400 grit or finer polishing cloth while rotor is being rotated. Slip rings may be lathe turned to maximum indicator reading of .002" (.05mm). Slip rings are not replaceable. Replace rotor if slip rings are excessively damaged. Inspect brushes for wear; replace if they are worn to less than 50% of original length.

SPECIFICATIONS

ALTERNATOR IDENTIFICATION & OUTPUT

See also:
• TROUBLE SHOOTING - BASIC PROCEDURES
• ALTERNATOR IDENTIFICATION & OUTPUT
• BENCH TESTING