Mort

I think the '03 alternator is rated at 105 amps according to the specification sheet I have.

KySilverado

iTrader: (7)

I've found listing for 145 and 105 amp available in the 03. Gotta get out to my glove box!

JK021500HD

I have a 2002 1500HD and I just called a dealer service dept and gave them my vin and I had a 105 amp. I got an alt from allen (Nelson) a brand new 145 amp from an escalade for like $174 shipped! I thought it was a great deal and I fit great on my 6.0 with a new longer belt. He said he got a palet of them so maybe he still has some left.

JK

KySilverado

iTrader: (7)

I just checked my option codes from the glovebox. I too have the 105 amp alternator. The 145 amp is an option in 03 that I didn't get. Looks like I'll be giving Allen and others a call for the 145 amp or larger?

Thanks all for the input. I will followup to this thread once I get new ALT in and let you know how it worked.

CRAZYCUTER4.8

iTrader: (2)

the new 05's have a different voltage control system, here is the info

Cooling Fan Control - Two Fan System
The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood fuse block.

During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the low speed fan relay coil, closes the relay contacts, and supplies battery positive voltage from the low fan fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan s/p relay and the right cooling fan. The result is a series circuit with both fans running at low speed.

During high speed operation the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. After a 3 second delay, the PCM supplies a ground path for the high speed fan relay and the cooling fan s/p relay through the high speed cooling fan relay control circuit. This energizes the cooling fan s/p relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the high speed fan relay coil is energized closing the relay contacts and provides battery positive voltage from the high fan fuse on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.


Important
The right and left cooling fan connectors are interchangeable. When servicing the fans be sure that the connectors are plugged into the correct fan.


The PCM commands the low speed cooling fans ON under the following conditions:

Engine coolant temperature exceeds approximately 94.5°C (202°F).
A/C refrigerant pressure exceeds 1447 kPa (210 psi).
After the vehicle is shut OFF if the engine coolant temperature at key-off is greater than 101°C (214°F) the low speed fans will run for a minimum of 60 seconds After 60 seconds, if the coolant temperature drops below 101°C (214°F) the fans will shut OFF. The fans will automatically shut OFF after 3 min. regardless of coolant temperature.
The PCM commands the high speed fans ON under the following conditions:

Engine coolant temperature exceeds approximately 104.25°C (220°F).
A/C refrigerant pressure exceeds approximately 1824 kPa (265 psi).
When certain DTCs set.
At idle and very low vehicle speeds the cooling fans are only allowed to increase in speed if required. This insures idle stability by preventing the fans from cycling between high and low speed.

Coolant Level Control (If Equipped)
Document ID# 1467477
2005 Chevrolet Chevy C Silverado - 2WD


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Charging System Description and Operation (Generator/Battery Control Module)
Electrical Power Management (EPM) Overview
The electrical power management (EPM) system is designed to monitor and control the charging system and send diagnostic messages to alert the driver of possible problems with the battery and generator. This EPM system primarily utilizes existing on-board computer capability to maximize the effectiveness of the generator, to manage the load, improve battery state-of-charge (SOC) and life, and minimize the system's impact on fuel economy. The EPM system performs 3 functions:

It monitors the battery voltage and estimates the battery condition.
It takes corrective actions by adjusting the regulated voltage.
It performs diagnostics and driver notification.
The battery condition is estimated during key-off and during key-on. During key-off the SOC of the battery is determined by measuring the open-circuit voltage. The SOC is a function of the acid concentration and the internal resistance of the battery, and is estimated by reading the battery open-circuit-voltage when the battery has been at rest for several hours.

The SOC can be used as a diagnostic tool to tell the customer or the dealer the condition of the battery. Throughout key-on the algorithm continuously estimates SOC based on adjusted net amp hours, battery capacity, initial SOC, and temperature.

While running, the battery degree of discharge is primarily determined by a battery current sensor, which is integrated to obtain net amp hours.

In addition, the EPM function is designed to perform regulated voltage control (RVC) to improve battery SOC, battery life, and fuel economy. This is accomplished by using knowledge of the battery's SOC and temperature to set the charging voltage to an optimum battery voltage level for recharging without detriment to battery life.

The Charging System Description and Operation is divided into 3 sections. The first section describes the charging system components and their integration into the EPM. The second section describes charging system operation. The third section describes the instrument panel cluster operation of the charge indicator, driver information center messages and voltmeter operation.

Charging System Components
Generator
The generator is a serviceable component. If there is a diagnosed failure of the generator it must be replaced as an assembly. The engine drive belt drives the generator. When the rotor is spun it induces an alternating current (AC) into the stator windings. The AC voltage is then sent through a series of diodes for rectification. The rectified voltage has been converted into a direct current (DC) for use by the vehicles electrical system to maintain electrical loads and the battery charge. The voltage regulator integral to the generator controls the output of the generator. It is not serviceable. The voltage regulator controls the amount of current provided to the rotor. If the generator has field control circuit failure, the generator defaults to an output voltage of 13.8 volts.

Generator Battery Control Module
The generator battery control module is a class 2 device. It communicates with the powertrain control module (PCM), instrument panel cluster and the body control module for electrical power management (EPM) operation. It is a serviceable component that is connected to the negative battery cable at the battery. It directly controls the generator field control circuit input to the generator. It monitors the generator field duty cycle signal circuit, its internal battery current sensor, the battery positive voltage circuit, and estimated battery temperature to determine battery state of charge (SOC). If the generator battery control module losses communication with other modules that provides input to it the default voltage will be set to XX volts.

Powertrain Control Module (PCM)
The PCM provides information over the class 2 serial data circuit to the generator battery control module. The generator battery control module monitors the following data parameters provided by the PCM:

Intake air temperature
Fuel grams per second
Throttle position
Engine cooling fan speed
Engine coolant temperature
The generator battery control module uses these data parameters for different charging system modes depending on the required voltage needed.

Instrument Panel Cluster (IPC)
The instrument panel cluster (IPC) provides a means of customer notification in case of a failure and a voltmeter. There is two means of notification, a charge indicator and a driver information center message of SERVICE CHARGING SYSTEM and CHARGING SYSTEM FAULT.

Charging System Operation
The generator battery control module controls the generator through the generator field control circuit. It monitors the generator performance though the generator field duty cycle signal circuit and the battery positive voltage circuit. The generator battery control module controls the generator through the generator field control circuit. The signal is a 5-volt pulse width modulation (PWM) signal of 128 Hz with a duty cycle of 0-100 percent. Normal duty cycle is between 5-95 percent. Between 0-5 percent and 95-100 percent are for diagnostic purposes. The following table shows the commanded duty cycle and output voltage of the generator:

Commanded Duty Cycle
Generator Output Voltage

10%
11.0 V

20%
11.56 V

30%
12.12 V

40%
12.68 V

50%
13.25 V

60%
13.81 V

70%
14.37 V

80%
14.94 V

90%
15.5 V


The generator provides a feedback signal of the generator voltage output through the generator field duty cycle signal circuit to the generator battery control module. The signal is a 5-volt PWM signal of 128 Hz with a duty cycle of 0-100 percent. Normal duty cycle is between 5-99 percent. Between 0-5 percent and 100 percent are for diagnostic purposes.

Charge Mode
The generator battery control module will enter Charge Mode when ever one of the following conditions are met:

The interpreted fuel rate is greater than 21 g/s and the throttle position is greater than 90 percent.
The headlamps are ON low or high beam.
The wipers are ON for more than 8 seconds.
The electric cooling fans are on high speed.
The rear defogger is ON.
Once one of these conditions are met the generator battery control module will set the targeted generator output voltage to 13.4 volts and then ramp that voltage up to 14.5 volts at a rate of 50 mV per second.

CRAZYCUTER4.8

iTrader: (2)

I could not paste everthing, but there is a voltage control module that is regulating voltage, the output in 05 is greater as well

VortechC5

iTrader: (6)

What is the option code? I am curious which one my 03 has.

Thanks.

KySilverado

iTrader: (7)

From memory believe it is was 8C6 for the 145 amp alternator. I'll reply later if incorrect. Working and the truck and info at home.

Mort

K65 = Alternator, 105 amps
K68 = Alternator, 105 amps | 2003
KG3 = Alternator, 145 amps | 1500HD

KySilverado

iTrader: (7)

Yep, My info is the same and the document I have also lists 145 amp alternator with an 8C6 option. I have the K68 for now.