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Alternator going bad?

JohnnieMo

SM 2017
PM 2014
SM 2013
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Over the past while I've noticed my voltage gauge on my 2008 LTZ is showing well under 14 volts while on the highway.  Other times it is up well over 14V.  I would say it is swinging from 12.5 up to 15 while the truck is running.  Is this a sign of an alternator about to give up?  I'm contemplating replacing it for insurance reasons, but I'm curious if fellow Avy owners have any knowledge on this subject.

If a replacement is warranted, do you have a suggestion?  Amperage? 
 
From what I've read, the ecm controls the voltage, but one constant is that with the lights on, or in tow/haul, it should remain at 14V minimum....mine does move around as well, but under those 2 conditions, it does stabilize.....
 
Is this a current thing that just started or has those readings been constant since you owed the AV?

I seem to remember in an older thread that GM had starting changing alternator usage to try and get better gas mileage figures. ( The less the alternator runs the less strain on motor.) So in effect on late model AVs the dip in the readings is normal according to that thread.

Check this thread:

http://www.chevyavalanchefanclub.com/cafcna/index.php/topic,150266.0.html
 
Vaeagleav said:
Is this a current thing that just started or has those readings been constant since you owed the AV?

I seem to remember in an older thread that GM had starting changing alternator usage to try and get better gas mileage figures. ( The less the alternator runs the less strain on motor.) So in effect on late model AVs the dip in the readings is normal according to that thread.

Check this thread:

http://www.chevyavalanchefanclub.com/cafcna/index.php/topic,150266.0.html

That link is awesome.  That verifies what I've been seeing. 

I first saw the issue last spring when I was running a 120V / 1400 watt AC inverter connected right on the battery.  The truck was just idling and the inverter kept losing power.  I checked the truck and the gauge was low.  However I forgot about it and noticed it again this weekend driving out to pick up our camper.  Once I connected the camper and was driving home, voltage was up again.  (However I was not in tow-haul mode)

If I see this again, I will immediately hit the tow/haul button and observe what happens. 

For the record I hate using tow/haul mode when towing as I find the torque converter never locks in and my trans temp skyrockets.  The supercharger makes up for that inconvenience.

Thanks everyone!
 
My alternator does this as well.  I have only had my truck for about 3 weeks now and am concerned that the alternator is bad.  I'm just going to keep an eye on mine for awhile.  If I do have to replace, at least it looks pretty easy to do.
 
jmcclung11 said:
My alternator does this as well.  I have only had my truck for about 3 weeks now and am concerned that the alternator is bad.  I'm just going to keep an eye on mine for awhile.  If I do have to replace, at least it looks pretty easy to do.

Read the linked thread above.  This is normal behavior and not something to be concerned about.  Saved myself a few hundred bucks!
 
I'd like to chime in here on this topic especially since my same issue thread was referenced in this thread.  I'll keep it short but, when I had my alternator and battery checked out the shop stated that everything was operating normal and shortly after that the gauge seemed to level off at it's usual spot right around the 14.5 mark.  This past spring I had a rod bearing spin and it then developed piston slap in the same cylinder as well as a collapsing lifter.  When they pulled the old motor and started transferring things to the new motor they discovered that the wiring going to the alternator was fried to a crisp and they could not even get the plug disconnected.  They ended up cutting off and repairing the wiring to the alternator as well as replacing the alternator.  My thinking is that maybe the wiring to the alternator is too light of a gauge and overheats a little each time and over time weakens the wiring?
 
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