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2008 silverado voltage drop

arctictwist

By arctictwist
in Ask A GM Technician

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arctictwist Enthusiast

arctictwist

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First, background. Truck has had the big 3 upgrade and an optima yellow top for 4.5 yrs. alternator is stock. Stereo isnt crazy, just a 1200 watt sub and 360 w speaker amp. My voltage always read around 12 but when i did the big 3 it shot up to a little over 14.

 

So yesterday im in traffic driving to work and i start getting abs and stabilitrack warnings. And i noticed the voltage was dropping. It dipped quick to the 11.5 line and then went back up a little. Maybe 12.5/13? I turned off everything and continued to work. The voltage stayed there.

 

A few hours later i started it up. No problem. Battery charged right up to ~14.4 so i turned it off. Morning comes and its time to go home. Again starts right up, charges right up, everythint is fine till i get off the highway. As soon as i stop at the light it happens. I stop in the store for a few minutes. Come out and again starts and charges right up. Happens again a couple minutes down the road. Then it hit me, it starts when i get to 210 degrees.

 

So today i drive to the gym, no problems until i hit 210.

 

So logically im thinking the radiator fans are causing the voltage drop.

 

How can i further diagnose, is my logic sound or am i totally off on the possible cause? Thanks.

 

Ken

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted

I would first connect a known good voltmeter to the battery directly and monitor voltage that way.

arctictwist Enthusiast

arctictwist

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I would first connect a known good voltmeter to the battery directly and monitor voltage that way.

i got 12.65 on the battery when the truck was off and 14.35 when it was on. However, the voltage in the car did drop like before a few more times and even did it once when the truck was not even up to temp yet... so there goes my fan theory.

arctictwist Enthusiast

arctictwist

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Okay dropped again, cleaned up grounds, did nothing. Testing right at the alt at 13 v now and 12.95 at the battery when its running. Im just gonna order an alt before it goes.

  • 3 weeks later...
arctictwist Enthusiast

arctictwist

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Posted

So update. Got my db electrical 200 amp alt in. Nothing changed except now when i start it, it goes over 15v for a min and my amps protect. I ran the live scan on my bluedriver and it ranged from 10.2 to 14.6 was the highest. This was after driving for a min so i didnt get that 15 volt beginning but have run it quick at start just to see. Now i also noticed at one point the volts spiked to 33 and the coolant temp spiked to 298. Just for a second. Obviously neither of those were real. I dont know if that helps anyone with ideas. This weekend i am pulling all my battery connections and big 3 upgrades and redoing them. New cable ends and making sure i clean up the body contact on the grounds the best i can. I already went through them once and thought i was good. But well see how it goes this time around.

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