2008 Chevy Silverado Alternator Charge Question

Tiny
JKBEAUMONT1
  • MEMBER
  • 2008 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 12,000 MILES
When cold, my alternator charges around 14.5 to 14.9 volts. When everything warms up, it drops to about 13 volts. Is this normal behavior for this alternator? And how do I find the max amp output of this alternator? It's on a 175AMP fused line to the battery and I think I read somewhere that it's max amperage was 165AMPs. Thanks!
Do you
have the same problem?
Yes
No
Saturday, May 30th, 2009 AT 4:42 PM

3 Replies

Tiny
IMPALASS
  • EXPERT
Hello -

I would say this is very normal. Remember while the truck is sitting other things are still "slightly" drawing a little current. Plus the battery is sitting slowly going down....

So when you first start....that is normal for it to take a little more charge. Circuits are cold, many things are charging up, You use the battery to start the vehicle....that is a big draw.

Then as you use thing the alternator will cycle giving you more/less power as needed. Here is a chart to help.

The engine control module (ECM) controls the generator through the generator turn on signal. It monitors the generator performance though the generator field duty cycle signal 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:


http://www.2carpros.com/forum/automotive_pictures/248015_Picture1_73.jpg



Unless you have a DTC or are experiencing some problems.......I would not be concerned.
Was this
answer
helpful?
Yes
No
Saturday, May 30th, 2009 AT 5:43 PM
Tiny
BRIAN 1
  • MEMBER
Here is some info;Charge Mode
The BCM will enter Charge Mode when ever one of the following conditions are met.

" The wipers are ON for more than 3 seconds.

" The GMLAN Climate Control Voltage Boost Mode Request is true, as sensed by the HVAC control head. High speed cooling fan, rear defogger and HVAC high speed blower operation can cause the BCM to enter the Charge Mode.

" The estimated battery temperature is less than 0 C (32 F).

" Battery state of charge is less than 80 percent.

" Vehicle speed is greater than 145 km/h (90 mph)

" Current sensor fault exists

" System voltage was determined to be below 12.56 volts

" Tow/Haul mode is enabled

When any one of these conditions is met, the system will set targeted generator output voltage to a charging voltage between 13.9-15.5 volts, depending on the battery state of charge and estimated battery temperature. Battery Voltage Gauge Operation
The IPC displays the system voltage as received from the BCM over the GMLAN serial data circuit. If there is no communication with the BCM then the gauge will indicate minimum.

This vehicle is equipped with a regulated voltage control (RVC) system. This system turns off the generator when it is not required in order to improve fuel economy. The generator will turn back on when additional voltage is required. This will cause the voltmeter to fluctuate between 12 and 14 volts as opposed to non-regulated systems which usually maintain a more consistent reading of 14 volts. This fluctuation with the RVC system is normal system operation and NO repairs should be attempted. For max output of the alternator is 145 amp with KG3 or 160 amp with KW1, these are the RPO codes located in the glove box just check and see if it has kw1 or kg3 and that will tell you.
Was this
answer
helpful?
Yes
No
+1
Saturday, May 30th, 2009 AT 5:47 PM
Tiny
JKBEAUMONT1
  • MEMBER
Awesome! That makes perfect sense. Interesting with regards to the RVC. Thanks again!
Was this
answer
helpful?
Yes
No
Saturday, May 30th, 2009 AT 5:51 PM

Please login or register to post a reply.

Recommended Guides