Alternator & Regulator - Except 120 Amp Cadillac Brougham I

DESCRIPTION

Delco-Remy CS121 (74-amp) and CS130 (85, 100 and 105-amp) alternators are used on most General Motors vehicles. The CS alternator uses a regulator which has built-in fault detection monitored by the ECM. A diode trio or regulator test hole is not included. Regulator is enclosed in a solid mold, mounted inside the alternator. Alternator is not serviceable. If alternator is defective, a new unit must be installed.

OPERATION

Unlike 3 wire alternators, this alternator may be used with only 2 connections, battery positive and an "L" terminal to charge the indicator bulb. Use of "P", "F" and "S" terminals is optional. The "P" terminal is connected to the stator and may be connected externally to a tachometer. The "F" terminal is connected internally to field positive and may be used as a fault indicator. The "S" terminal may be connected externally to battery voltage to sense voltage to be controlled. (Scheme 1)

Scheme 1

Note. Manufacturer does not recommend disassembling and servicing CS alternators. If alternator is defective, a new unit must be installed.

ADJUSTMENTS

No adjustment or maintenance is required on alternator assembly. Regulator voltage is preset and no adjustment is provided.

TROUBLE SHOOTING

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

ALTERNATOR WARNING LIGHT

1. Visually check alternator belt and wiring. On models without charge light, proceed to «UNDER OR OVERCHARGED BATTERY»(/cadillac/brougham/i-1987-1992/remont/charging-system/#alternator-regulator-except-120-amp__under-or-overcharged-battery). Turn ignition switch to the "ON" position (engine not running). Charge light should come on.
2. If charge light is not on, disconnect alternator harness plug at alternator. Using a jumper wire, connect one end of jumper wire to alternator harness plug terminal "L" (Brown wire) and connect other end to ground. (Scheme 2) If charge light comes on, replace alternator.
3. If charge light does not come on, locate open circuit between grounding lead and ignition switch. Charge light may be open.
4. Start engine and reduce speed to idle. Charge light should go off. If charge light stays on, disconnect alternator wiring plug. If light goes off, replace alternator.
5. If light stays on, check for grounded wire to alternator wiring plug terminal "L".

Scheme 2

UNDER OR OVERCHARGED BATTERY

1. If battery is undercharged or overcharged, disconnect alternator wiring plug from alternator.
2. Using a voltmeter, connect positive voltmeter lead to "L" terminal of alternator wiring plug and negative lead to ground. (Scheme 2) Turn ignition switch to "ON" position (engine not running).
3. If voltmeter reads 0 volt, an open between "L" terminal and battery is indicated. Repair as required. Reconnect alternator wiring plug.
4. Using a voltmeter, connect positive voltmeter lead to positive battery post and negative lead to negative battery post. Start engine and run at moderate speed. If voltage reads more than 16 volts, replace alternator.

CURRENT OUTPUT TEST

1. Using an ammeter, connect ammeter in series with positive battery cable. Using a voltmeter, connect positive voltmeter lead to positive battery post and negative lead to negative battery post. Connect carbon pile rheostat to battery. Ensure carbon pile rheostat is in the "OFF" position before connecting to battery.
2. Start engine and reduce speed to idle. Turn on all accessories. Load battery with carbon pile rheostat to obtain maximum amperage. Maintain voltage at 13 volts or more.
3. If ammeter reads within 15 amps of rated output, alternator is okay. If ammeter does not read within 15 amps of rated output, replace alternator. See the «ALTERNATOR SPECIFICATIONS»(/cadillac/brougham/i-1987-1992/remont/charging-system/#alternator-regulator-except-120-amp) at end of this article.

BENCH TESTS

1. Mount alternator on test stand. Make connections as shown in charging system wiring diagram. (Scheme 3) Leave carbon pile disconnected. Ground polarity of alternator and battery must be the same. Ensure battery is fully charged. Use a 30-500 ohm resistor between battery and terminal "L".
2. Rotate alternator by hand in clockwise direction. Slowly increase alternator speed and observe voltage. If voltage is uncontrolled and increases to more than 16 volts, rotor field is shorted and/or regulator is defective. A shorted rotor field coil can cause the regulator to become defective.
3. If voltage is less than 16 volts, increase speed and adjust carbon pile to obtain maximum amperage output. Maintain voltage at 13 volts. If output is within 15 amps of rated output, alternator is okay. If output is not within 15 amps of rated output, replace alternator. See «ALTERNATOR SPECIFICATIONS»(/cadillac/brougham/i-1987-1992/remont/charging-system/#alternator-regulator-except-120-amp) at end of article.

Scheme 3

OVERHAUL

Overhaul information is not available.

ALTERNATOR SPECIFICATIONS

ALTERNATOR SPECIFICATIONS

See also:
• TROUBLE SHOOTING - BASIC PROCEDURES
• UNDER OR OVERCHARGED BATTERY
• ALTERNATOR SPECIFICATIONS