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2003 chevy trailblazer_ltz
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8 Posts
Discussion Starter #1
Hey everyone,

I had a quick question and possibly a concern.

It has been really cold here lately (17 degrees on average, 9 last night:)) and when I started it last night, I noticed the lights were dim, and about 2-3 seconds later it brightened up.

Same thing happened today before work, I got in, watched the Ammeter, and it hung around 12v for about 3 seconds, then went up and everything brightened.

It did the same thing tonight, for a bit longer, say, 6-7 seconds. It just seems like the alternator has to "warm up", but that doesn't make any sense, does it?

And ive stopped, started it after the engine is warm, does just fine like it normally does, straight to 14v after starting.

Like I said its been below 30 degrees each time Ive tried this.

Thanks for your help ahead of time!
 

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2005 chevy trailblazer_ls_ext
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2,667 Posts
I think we discussed this a couple of years ago. The consensus was that it was normal. I don't remember why - maybe someone with a better memory or more knowledge than I do will chime in here.
My 05 has done that from day 1. Three dealerships all said "Normal operation".
 

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2002 olds bravada
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2,369 Posts
i'm having the same problems, but only if them temp is below 10 degrees. i can't figure out what would be causing this other than the alternator..but i may be wrong.
 

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2003 chevy trailblazer_ltz
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Discussion Starter #4
Yea, it seems alternator-ish.

Like it has to turn a few times before putting out voltage.
 

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2003 chevy trailblazer_lt_ext
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26 Posts
I've got the same problem....it's been doing it since I bought it in early 2006...I wish I knew why, but it hasn't caused a problem yet....I'm just waiting for one of these mornings for it to not put out any juice at all...

Later
Phil
 

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2009
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1,088 Posts
Mine does this also. It has been my understanding that the voltage regulator is built into the PCM so I figured that it was the PCM limiting current at startup. I could be way off. Who knows.
 

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2003 chevy trailblazer_ls
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5,267 Posts
the computer on the newer cars is able to control the load on the engine...
the alternator is a load when its running.
I think that it keeps the alternator off during engine startup to lessen the load. engine runs on battery power for a bit...
it then turns on the alternator to supply power.
While this is done I think whats happening is that the cold weather is reducing battery output and when the alternator comes on... you really see the output increase....
 

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2003 chevy trailblazer_ltz
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8 Posts
Discussion Starter #8
well, the thing about it is, is that a battery outputs 12v constantly, and when its warmer outside, or when the truck is already warmed up, it doesn't do it.

normally after starting it hits 14v immediately, i just happened to notice it the first time because everything got brighter, then the next few times i kept on eye on the ammeter and noticed it just suddenly change.
 

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2002 chevy trailblazer_ltz
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If what rbarrios is saying is true about the PCM being able to limit alternator output depending on the temp., then what your seeing is "normal".

Cold weather, a cold battery, thicker fluids (oil, etc), all put extra strain on the starting system, and if the PCM is "smart" enough to shut off, or lower the alternator output for a few seconds during start-up, then that could be what your seeing.

It would also explain why you don't notice it during the warm weather.

Keep an eye on it for a while after you start it in cold weather, but as long as it only last a few seconds, I wouldn't be too concerned.
 
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