When I start my engine in the morning I have noticed that a few seconds after it starts the voltage dips down below 12 for about two seconds, then returns back to normal. Sometimes it happens a second time after a few more seconds. Is this normal? Is it some sort of test that the vehicle computer is performing on the electrical system?

 

might be something new about these 6.7's and the relays kicking on and off.

 

Maybe it was cool enough the heating grid was kicking on and off. Mine does the same thing and really kills the voltage.

 

intake heater going on and off

 

sounds like the intake heater.

 

I just did a post on this this mourning titled Alternator ? cause mine was doin the same thing we came to the conclusion it was just the grid heater like everyone is saying....

 

it is what everyone is saying. The cummins relies on 2 stacked intake grid heaters for cold (and colder) starting. Each grid heater draws approx 50-60 amps (this means 120 amps). Add to this the other electrical demands just to run the engine and truck (ignintion, abs, etc) and you far exceed the capable output of the alternator (probably 150 amps @ a couple thousand RPM) as alternators do not charge well at idle. So by exceeding the alternator you begin to draw on the batterys which are capable of approx 12.6 volt in perfect conditions. In other words, normal operation

 

Yes definitely intake grid. The powerstrokes I work on do the exact same thing, cept you know glowplugs and not heater grid.

 

Mine does the same, if you have your headlights on as well you will see thme dim... Heater grid

 

Kinda the same question I have. Mine ( an 06 ) started doin this about a month ago. Now when I turn the key to warm the glow plugs the voltmeter is almost down near 8. before it was around the normal 12. Seeing that it stays around 8 on startup, even if I have been runing for an hour stop for a few minutes and start up again. It does the same thing, keeps getting lower on the voltmeter. I am hoping it is the heater like mentioned above, but thinking it could be the alternator. Just confuses me why the voltmeter keeps getting lower and lower, day after day? Confused CTD owner.