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I have a 2012 Chevy Silverado 1500 with the 6.2L. My voltage is 14.45v running around town but when I drive it for long distances or I let it idle for 10 minutes or more it drops to 12.67v and stays there. Yesterday I drove it for an hour and it dropped to 12.67v got to my appointment and when I came out 45 min later it said start vehicle battery low so I ran it for 20 min and shut it off and about 2 hours later it was still at 12.67v. I have put a 160 amp alternator on it from gm this is my 4 or 5 alternator. Any ideas?

Edited by Boomer1974!
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Make sure the belt tensioner is up to snuff.  A loose belt can cause all sorts of issues.  Also make sure your terminal connections are good and clean, take them off and check the inside where it meets the battery. 

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21 hours ago, Boomer1974! said:

Thank you for your reply but those have already been checked and secured and tensioner is good.

considering you have replaced this alternator 5 times, you might want to get those rechecked.  Alternators have a built in voltage regulator for how much amps they put out, so very little on the truck body side can effect its short life span that you are experiencing. A dead short is possible,  or a parasitic draw but I wouldn't expect that to ruin your alternator.   You can try to remove a fuse at a time of non essential things like heater or ac, radio etc and see if this helps with your issue. If it were me based on how many miles you have run, and the amount of alternators you have put in,  I would replace the belt tensioner with a new one, if it doesnt change your issue, take it back. 

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On 4/13/2021 at 7:53 PM, Boomer1974! said:

I have a 2012 Chevy Silverado 1500 with the 6.2L. My voltage is 14.45v running around town but when I drive it for long distances or I let it idle for 10 minutes or more it drops to 12.67v and stays there. Yesterday I drove it for an hour and it dropped to 12.67v got to my appointment and when I came out 45 min later it said start vehicle battery low so I ran it for 20 min and shut it off and about 2 hours later it was still at 12.67v. I have put a 160 amp alternator on it from gm this is my 4 or 5 alternator. Any ideas?

The computer controls the output of the alternator and it seems to me that you need a new battery regardless of how it tests out.  These computer systems don't take kindly to aftermarket parts so make sure to use GM OE or ACDelco Professional parts.

 

Is your Silvy an NHT with 3.73 gears?

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1 hour ago, Boomer1974! said:

Swathdiver it is a 2012 Chevy Silverado 1500 crew cab with 6.2 L  with 3.73 gears with a 6 in lift 325/60R20 BFG MT

My daughter just bought one; loves the 6.2 and NHTs 3.73 gears and it has a Zone 6.5 lift running 35x12.5x18s with Nitto mud tires for now.  

 

Curious, what kind of mileage are you getting and did you recalibrate the speedometer?  She averaged 15 mpg on the highway on 91/93 and gets about 9 mpg burning straight E85 in mixed city/highway driving around town.

 

 

IMG_4258.jpg

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ProComp 6 in I bought the truck last year already lifted it is a Tuscany conversion. Not sure on the calibration of speedometer. I am going to put a McGaughys 7-9 on it in about 6 months I am getting around 12.9-13.5 on the highway running 87 just switched to 89/91 so will have to get back with you after I run it for a bit. 

CEE44C6E-EE23-44DE-BC26-EA0F08ACA00E.jpeg

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Swathdiver I drove to a town 14 miles away last night and I was getting 15.4 mpg with switching to the 89 octane. Taking it to get windows tinted on Wednesday so we will see what kind of mpg I get then. The shop is about an hour away and then I will be driving to my daughters game and then home so I will be putting some miles on it then. Will keep you updated.

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