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2005 gmc envoy_sle_xl
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Discussion Starter · #1 ·
My 05 envoy xl 4.2 battery was having a hard time starting the car this morning, it was -9 out with windchills down to about -20. I jumped it and it started just fine so i decided to check the voltage of the alternator and it was reading at just over 15 volts, after I let it run for a little bit it dropped down to about 14.7. Should I be worried about that? Also could the battery be causing the high voltage when it’s that cold? The battery is about 5 years old so it probably wouldn’t hurt to get it tested anyways.
 

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2005 gmc envoy_sle_xl
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Discussion Starter · #3 ·
Can a bad battery cause high voltage from the alternator?
 

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2008 chevy trailblazer_lt
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62 Posts
Gm has rvc. Can go from 11 1/2 - 15.5 volts. I have a 2008 tb. I know mine does. If there is a problem the bcm will set a code and turn mil on. Have battery load tested. If battery is old then wouldn't be bad to replace it.
 

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2005 gmc envoy_sle_xl
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Discussion Starter · #5 ·
All the way up to 15.5? That’s interesting. I am definitely going to get the battery tested, I’ll probably just pick up a new one anyways since it has been having issues in this cold.
 

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2008 chevy trailblazer_lt
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When my tb is cold can see higher than normal charging voltage. You have the current sensor around negative battery terminal then you have rvc. I took a 2 hour course on it years ago. There's like 8 different modes.
 

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Discussion Starter · #7 ·
That’s great to know! Thank you so much for your help! The temps here have been well below zero the last week, so I guess that makes sense.
 

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2007 chevy
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My 05 envoy xl 4.2 battery was having a hard time starting the car this morning, it was -9 out with windchills down to about -20. I jumped it and it started just fine so i decided to check the voltage of the alternator and it was reading at just over 15 volts, after I let it run for a little bit it dropped down to about 14.7. Should I be worried about that? Also could the battery be causing the high voltage when it’s that cold? The battery is about 5 years old so it probably wouldn’t hurt to get it tested anyways.
That would make sense, since it has to use extra juice to crank when it's cold, the regulator will throw it back some extra Vs at first.
If the battery hasn't been taken out in 5 years, it might be worth cleaning the posts and connectors- and you could get another year out of it.

On the other hand- at this rate they might be 5x the price next winter :unsure:
 
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