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Alternator works when it wants to. Yesterday my car needed a jump because the battery died. While driving I noticed the volt meter was showing around 12.5. I get home and test the alternator and it was putting out 12.6. Ten mins later it was reading 14.7 and then back to 12.4. I thought it was wearing out so I replaced it. Today it's doing the same thing. Any ideas as to why? I am also now receiving OBII codes for low voltage on several systems.
 

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What year is your Traverse? (Sorry--just went back and saw title said it's a 2008 Acadia.) Later models (and I don't know when the change occurred, but I had a 2007 Pontiac Grand Prix that had a variable output alternator) have an alternator that provides output voltage as required by the systems' demands, and it will vary from approx 12.5 to approx 14.5 depending on the load. It's not like the old systems that produced a constant output thru a voltage regulator. The BCM ( I believe it's the BCM; one of the control modules) controls the output.
 

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Aaron C , you look too young to be driving. How old is the battery? What is your battery voltage after you shut off the engine? Where are you checking the alternator output voltage?
 

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My first guess is bad battery. If it's the original one, you've been EXTREMELY fortunate. But for a vehicle that could be almost 13 yrs old, you SHOULD be on about your 3rd battery by now.

Look up Battery Load Management in your owners manual. It's in Chapter 6, Lighting, in the 2011 Traverse manual. It explains why the alternator output may vary.
 

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Even a newer battery isn't always good. I replaced mine a year and three months ago, a walmart special. Mine drained when I was doing some modifications for a dashcam supply which the modules didn't agree with. One drain cycle and it didn't seem to hold a charge well after this, even after I put everything back the way it was, it went dead again. I replaced the battery and all is well, adjusted the modifications for the dashcam and no more issues.
 

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I have had my 2009 for ur years and replaced it three times, they simply such. the besy part is I bought the first one at the dealer and the next two are covered under warranty. the dealer doesn't aegue about replacement like other suppliers have in the past.
 
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