CHARGE INDICATOR LAMP DIAGNOSIS CHECK OUTLINED

VEHICLES AFFECTED: ALL 1986-1987 MODELS WITH 'CS' GENERATORS AND CHARGE INDICATOR LAMP (EXCEPT 'E/K' AND CADILLAC 'C' MODELS)

The "CS" of generator is easily identified by the regulator configuration to which the wiring harness is attached. Most "CS" regulators have four terminals, whereas the older "SI" regulator has only two terminals. Only a few minutes are required to quickly diagnose a "CS" charging system when the charge indicator lamp does not operate properly. Normally, with switch on, the lamp should come on, and then go out when the engine starts. If not, proceed as follows:

SWITCH ON, ENGINE STOPPED

1. If lamp is off, detach wiring connector at generator,carefully identify and ground "L" terminal. Use 5 amp fused jumper lead. NOTICE: Make contact only with "L" terminal.

2. If lamp does not come on, circuit between "L" terminal and ignition switch is open. Bulb may be open.

3. If lamp comes on, replace or repair generator.

SWITCH ON, ENGINE RUNNING AT MODERATE SPEED

1. If lamp is on, stop engine, turn switch on, and detach wiring connector at generator.

2. If lamp stays on, "L" terminal wire is grounded.

3. If lamp goes out, replace or repair generator.

These checks require no more than a few minutes to perform. If lamp operates normally, but the battery is undercharged or overcharged, check the battery and the generator for amperes output as covered in vehicle manufacturer's Service Manuals. Also, use the Service Manuals to check vehicles without a charge indicator lamp and the vehicle exceptions listed above.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.