charging issues

[DJanove]

On start up, on my 2005 2500 diesel,the dash volt meter shows around 12 volts.After a few minutes the meter rises to above 14 volts. using an external volt meter.while this is happening, it reads between 12.3v to approx 13v..after a few minutes, when the dash meter rises, my volt meter will then read around 14.5 volts..Could the problem be the voltage regulator. Is it in the alternator, or is it part of the PCM?

 

[petersonj]

I don't know how familiar you are with Cummins diesel engine operation.

What you are describing is normal for this engine. The intake manifold heaters will begin their post-cycling sequence after the engine is running. During their "on" cycle, the heaters will draw more current than the alternator can produce, consequently the lower voltage reading. Once a predetermined road speed is reached or the engine warms to a predetermined point, the intake manifold heater post-cycling will be switched off. Battery voltage will rise to its normal upper limit.

More information about your truck and your knowledge of maintenance and repairs of your truck would be helpful.

- John

 

[Ozymandias]

On start up, on my 2005 2500 diesel,the dash volt meter shows around 12 volts.After a few minutes the meter rises to above 14 volts. using an external volt meter.while this is happening, it reads between 12.3v to approx 13v..after a few minutes, when the dash meter rises, my volt meter will then read around 14.5 volts..Could the problem be the voltage regulator. Is it in the alternator, or is it part of the PCM?

The dash Shows what the BCM wants to show you, in other words the gauge is fake. Your system works as designed. Your measured numbers are good.

 

[Darkbloodmon]

Depending on how good your ears are you can hear the alternator load and unload with engine speed at idle during what you're describing.

Battery and Charging system health are pretty critical on these trucks because they do put a good stress test on your system during a cold start, even more so in the colder climates. I'm in the South FWIW.