How is the voltage regulated on a C5? Does the PCM have anything to do with it or is it controlled by the voltage regulator in the alternator?

 

Voltage regulator in the alternator.

 

14.2 +/-

 

+/- what? 5%, 10%.....

 

My voltage varies from 13.2-13.8 57k on it

 

00 coupe / 100k miles, 14.4 or about 13.6 with headlights on after HID conversion

 

Sounds to me like you're in the normal range.

 

Yup, starts off at about 14.1 and runs down once the initial load is over. Ends up about 13.8+

 

YEP, I have two 2002 C5's with 35k & 29k miles with same HID lights and get those same volt readings.

 

If most of you are getting more voltage than me, I wonder if its time for a new alternator? I priced a powermaster and it was $800

 

Nope. That alternator will not give you "more voltage". Handle a much higher current load? Yes.
You may just need a little ground cleaning here a than there but you're still within the normal voltage range.

 

It depends on what year car you have since GM made changes somewhere between 99 and 03. For a 2003 this is how the charging system works:

Charging System Description and Operation
Generator
The Valeo generator is electrically similar to earlier models. The generator features the following major components:

The delta stator
The rectifier bridge
The rotor with slip rings and brushes
A conventional pulley
The regulator
The pulley and the fan cool the slip ring and the frame.

The generator features permanently lubricated bearings. Service should only include tightening of mount components. Otherwise, replace the generator as a complete unit.

Regulator
The voltage regulator controls the rotor field current in order to limit the system voltage. When the field current is on, the regulator switches the current on and off at a rate of 400 cycles per second in order to perform the following functions:

Radio noise control
Obtain the correct average current needed for proper system voltage control
At high speeds, the on-time may be 10 percent with the off-time at 90 percent. At low speeds, the on-time may be 90 percent and the off-time 10 percent.

Circuit Description
The generator provides voltage to operate the vehicle's electrical system and to charge its battery. A magnetic field is created when current flows through the rotor. This field rotates as the rotor is driven by the engine, creating an AC voltage in the stator windings. The AC voltage is converted to DC by the rectifier bridge and is supplied to the electrical system at the battery terminal.

When the engine is running, the generator turn-on signal is sent to the generator from the PCM, turning on the regulator. The generator's voltage regulator controls current to the rotor, thereby controlling the output voltage. The rotor current is proportional to the electrical pulse width supplied by the regulator. When the engine is started, the regulator senses generator rotation by detecting AC voltage at the stator through an internal wire. Once the engine is running, the regulator varies the field current by controlling the pulse width. This regulates the generator output voltage for proper battery charging and electrical system operation. The generator F terminal is connected internally to the voltage regulator and externally to the PCM. When the voltage regulator detects a charging system problem, it grounds this circuit to signal the PCM that a problem exists. The PCM monitors the generator field duty cycle signal circuit. The system voltage sense circuit receives B+ voltage that is Hot At All Times through a fuse link that is connected to the starter. This voltage is used by the regulator as the reference for system voltage control.

Charging System Indicator(s)
CHARGE SYSTEM FAULT
The IPC illuminates the CHARGE SYSTEM FAULT indicator in the message center when the following occurs:

The PCM detects that there is a problem with the electrical charging system. The IPC receives a class 2 message from the PCM.
If the tachometer is less than 500 RPM and the power mode state is in the crank mode then this message will not be displayed. Instead the CHECK GAGES indicator will illuminate.
HIGH VOLTAGE
The IPC illuminates the HIGH VOLTAGE indicator in the message center when the IPC detects that the ignition is in RUN and battery voltage is greater than 15.75 V for more than 5 seconds.

LOW VOLTAGE
The IPC illuminates the LOW VOLTAGE indicator in the message center when the IPC detects that the ignition is in RUN and battery voltage is less than 10 V for more than 5 seconds.


Bill