Indicator Light

[yogi_123rd]

The low voltage red indicator light on my 94 PA occationally comes on (sporatically), but the voltage gage always reads charging. Is there a wire I can check? Bad ground?? How does the indicator light come on?

[jag_man653]

Originally Posted by yogi_123rd

The low voltage red indicator light on my 94 PA occationally comes on (sporatically), but the voltage gage always reads charging. Is there a wire I can check? Bad ground?? How does the indicator light come on?

Mine does too. It's a '95 PA Ultra. The light comes on sometimes at startup, and stays on for varying times. Sometimes just 10-20 seconds, sometimes for a block of driving. Had the shop check the alternator and battery, under load, and they could find nothing wrong. Also, I believe it's not holding voltage as well as it used to. Sometimes dead center, sometims up a few notches on the gauge.

Ed

[HotZ28]

The indicator lamp should come when the ignition switch is turned on. If it does not come on, or is burned out, there is a 500 ohm resistor in the circuit to allow a bypass of the light. The plug on the back of the alternator has terminals marked as I-L-P-& S.

The P terminal is the phase connection and is only used to send a signal to a relay or frequency sensing tachometer. There may not be a wire leading to this terminal. This is normal.

The L terminal is for the indicator lamp. When used, this terminal is connected to the vehicle’s indicator lamp. A 300 to 500 ohm resistor is connected across the lamp to provide a “start charging” signal if the lamp burns out. Note that terminal I may be used, as described, instead of terminal L.

The I terminal is used for the ignition terminal. When used, this terminal is connected to the vehicle’s ignition switch. Note that terminal L may be used, as described, instead of terminal I.

S terminal is to sense battery voltage. When used, this terminal provides the alternator with a precise battery voltage reading. If this terminal is not used, the CS series alternators use the battery terminal as a voltage reference.

GM uses several wiring configurations for this alternator. Note that terminal I and L activate the alternator. The alternator will not charge without voltage present at I, L, or both I and L.

The "BAT" post on this alternator must receive at least twelve volts before the regulator will allow the alternator to charge. If there is less than twelve volts at this post, check the battery, BAT wire, and fusible links.

The CS series alternator is capable of extremely high current output for its size. As a result, it is especially prone to damage by defective batteries. In fact, most alternator failures are caused by defective/discharged batteries, loose drive belts, or corroded wires.