No Alternator output on start up 2008 Silverado 6.6 LMM

[EdSpaek]

Did some follow up to the thread from a few days ago where it was noted that the dash voltmeter showed only battery voltage for several minutes then would indicate a charge-the thought was this was normal and the dash gauge may not be indicating properly

I attached my Fluke to the battery and it indicated 12.1volts prior to starting, started the vehicle and noted that the dash voltmeter indicted no charge and my Fluke verified that I only had a battery voltage of 11.2 volts.

Turning on the fan and headlights took me into the 10.9 range

After a few minutes the alternator began to charge and both voltmeters indicated 15.6 volts

There does appear to be an intermittent problem with the vehicle's

I will schedule into Chevy and advise

[Jake99Z71]

I believe this is the normal operation on the LMM trucks.

[Duramaster]

What part of the country are you located in? During a cold start the glow plugs and the IAH are on for a period of time causing a huge current draw on the electrical system. Do you have an inductive pickup for your fluke meter that reads in the 0 - 400 amp rang? If so, put it on the G/P power supply and check current draw. Do the same for the Intake Air Heater. Send me your E-Mail address in a private message and I will send you the info on the G/P and IAH operation.

[EdSpaek]

Duramaster

I am in the Chicago area-has only been in the mid thirties recently
I do have a high current clamp on for my fluke

[Rabbler]

Batteries sound weak. 12.1 Volts is pretty low.
Check them individually when disconnected. A good fully charged battery should read about 12.6 Volts.
Other than that it sounds normal.
Do the 07+ Diesel trucks have the smart charging systems (RVC)
that the gas truck have?

Your current clamp will read 400 amps? Wow!
Mine maxes at 80 amps...

[JohnC]

The alternator cannot keep up with the current draw on a cold start in cool or cold weather, especially at idle. Nothing to worry about.