Well im installing my 05 fans with the factory harness tommorrow; wait4meperformance is doing my tune so i told him to turn on pins 33 and 42 I will definetly post and let everybody know how it going and let you know if I get that voltage drop

 

That sounds good! Let us know how it turns out

 

Is there some sorta control from the PCM on the alternator?

I've noticed sometimes just cruising down the highway that the voltage will be "low" under 14 volts. The fans are not programmed to come on on the highway over 35mph so I know they aren't on.

Most of the time even at idle with the fans on the voltage is over 14 volts though, just seems to dip down sometimes while cruising down the road.

I've never figured it out.

 

I believe the 2005+ models have alternators that "turn off" when they're not needed and come back on when there's an amp draw. I read it was supposed to help fuel eco., im not really sure how it does that, but that's what it said....

 

Yeah, I thought I heard that before but, wasn't sure. I wish it helped fuel economy.....13mpg ain't gettin it.

Thanks

 

maybe without the "special" alternator you'd be getting 11mpg lol

 

Well i installed the efans and the factory harness on my 2004 escalade ext from a 2005 escalade i sent the pcm to get tuned from wait4me performance the fans come right on low with no volatge drop jesse did a great job pin 33 and 42 are turned on this of course was at idle in park with the a/c on and off there was no voltage drop i also replaced the alternator to a 145 amp alternator, if this helps i have a friend here who installed 05 fans on a 2000 denali and had the same promblem with voltage drop he just replaced the alternator pulley with a smaller diameter pulley his promblem went away. 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.

 

Well the only control from the pcm to the alternator is if your vehicle is equipped with a generator control module which started in 2005 and up otherwise the alternator works just liek a alternator suppossed to here is a description on that GCM
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, charge indicator control, input to the generator. It continuously monitors the generator field duty cycle signal circuit and the battery voltage. If the generator battery control module loses communication with the PCM, the default voltage will be set to 13.8 volts and the module will set U1016. If the generator battery control module loses communication with the body control module (BCM), the module will set U1064.

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

• Exterior Environment - Outside Air Temperature

The generator battery control module uses these data parameters for different charging system modes depending on the required voltage needed.

Charge Mode
The generator battery control module will enter Charge Mode when at least one of the following conditions is met:

• The electric cooling fans are on high speed.

• The rear defogger is ON.

• The battery state of charge is less than 80 percent.

• The battery current is not between -8 and 15 amps.

• The estimated ambient air temperature is less than 0°C.

• DTC B1516 is set.

Once one of these conditions are met the generator battery control module will set the targeted generator output voltage to the nominal optimum battery voltage which is from 13.9-15.5 volts, the voltage set point is based on the batteries state of charge and estimated battery temperature. The battery voltage ramps up to the targeted set point at a rate of 20 mV per second.

Fuel Economy Mode
The generator battery control module will enter Fuel Economy Mode when all of the following conditions are true:

• Estimated ambient air temperature is equal to or greater than 0°C (32°F).

• The calculated battery current is less than 15 amperes and greater than - 8 amperes.

• The battery state of charge is greater than or equal to 80 percent.

• The rear defoggers are turned OFF.

• The electric cooling fans are on low speed or OFF.

The targeted generator output voltage is 13 volts. The generator battery control module will exit this mode once the criteria are met for Charge Mode or it will boost voltage to a pre-determined set point for the fuel pump, headlamps, or windshield wipers.

 

^^That sounds good, I'm glad it worked out so well for you.

Is there any reason to get a Nelson Harness over a Factory harness, now that GM is making them?

 

In the PCM, there are settings that need to be entered for the required airflow of the fans, which affect the idle, which affect the voltage. On Camaros for example, you also see a slight voltage drop when the fans kick on high, which is absolutely normal. I didn't fully read the thread, and I hope this was lready covered, but how much voltage are you guys dropping? If it is 2 or 3, that is fine. Anything beyond the voltage dropping below 10, and that is not good. Also and overdrive alt pulley (like from ASP) can really help.