Charging issue

When I start my 2004 trailblazer the lights remain dim (Voltage at 12v) for about 15 seconds, then return to normal as I watch the voltage rise to 14v.
I just replaced the alternator since my TB has over 100k miles.
No codes show. Any Clues?
Thanks, Doug

Ok did it do this before you replaced the alt.?

Yes it did. I just assumed since it was the original alternator that it was on the way out.

Make sure the belt is not slipping if ok, then you will need a full scan to look at bcm and pcm inputs. Of course check all the ground and battery connections first then also confirm this is correct gage info using a tester right off the battery.

I also put a new serpentine belt on. I hear no "squeal". I can actually see the intensity of the headlights brighten just like a switch was being turned on. I will try a full reset tomorrow even though I see no codes displayed. I just have a basic Actron CP9125 reader.
P.S. I never see and fluctuation after the initial startup. No flicker..... nothing. Battery is original yet seems to crank over normally (by sound of things).

Do a load test on the battery, another thread regarding an Envoy same issue, turned out to be the battery.

Good idea on the battery. After all it is 5 years old.
Thanks Guys, Doug

Just an update. I replaced the battery. Symptoms continue. I took to the dealer and paid the $100 to have a test run. They found nothing wrong.
I am finding the delay is related to the temperature outside. The colder it is, the longer the delay. Today it is 15 deg and it took 20 seconds before the charge kicked in.
Could there be a relay in the charge system that may be sticking?
Thanks, Doug

According to the wiring diagram at AZ, repair guides, the pcm commands the charge start up process.

Ok, thank you. Hopefully it does not get worse or just quit altogether.

how cold is it outside. if its cold then the battery isn't fully charged overnight so there's a thing so that the alternator wont overheat or work too hard at intial start up. it is fine if it does this. nothing is going to happen

The outside temperature would be below 30 deg F. You may be right it is just a low level sort of protection.
Funny I have owned this TB since new and had never noticed it before.

Doug

how cold is it outside. if its cold then the battery isn't fully charged overnight so there's a thing so that the alternator wont overheat or work too hard at intial start up. it is fine if it does this. nothing is going to happen

do you have aftermarket headlamp bulbs?(blue or white light)? i have seen that they take a bit to warm up for full intensity.

I shut my headlights down before starting mainly because I have a lot of cool wildlife I do not want to disturb. They are Ok with me and the car starting.... just not flashing lights.

So anyway, that is not a factor. I have nothing high current set to come on at start. I still see a definite change in dash light intensity as well as the obvious deflection rise in the voltage gage. I get this same reading on my DVM plugged into the lighter plug. Hooking this directly at the battery and taking a reading in the dark is not very convenient.
I do know that there may be pumps, IE the one under the driver's floor that do run only under certain conditions. Perhaps a factor?

Doug

do you have aftermarket headlamp bulbs?(blue or white light)? i have seen that they take a bit to warm up for full intensity.