2011 Silverado 1500 - AC power to battery
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2011 Silverado 1500 - AC power to battery
Good morning!
I’ve got a 2011 Silverado 1500 4x4 with the 4.8 V8. It’s the WT model regular cab.
Ever since it’s gotten cold my battery has been draining over a period of a few days and I am un-able to start the truck.
The battery that I have is only a couple years old. When I disconnect the battery it holds its charge so I do not believe it’s the battery - although I never got it tested.
After doing some googling I tested the truck for parasitic draw but it’s only got a draw of around 0.15-0.17 amps. Even after keeping it hooked up for a few hours and overnight it’s not going above those numbers.
The alternator charges fine as well.
However I did come across something online that says if you’ve got AC power going to your battery that the diodes in the alternator are no good and should get replaced.
I checked to see if I had AC voltage going to the battery, and I had 30 volts going to it!
I replaced the alternator, checked it again and I’m still getting 30 volts AC to the battery.
What else can cause AC power going to the battery? Maybe it is this component that failed that is causing my battery to slowly drain?
Thank you so much for any ideas, because I am at a loss and ready to bring it in to the dealer.
I’ve got a 2011 Silverado 1500 4x4 with the 4.8 V8. It’s the WT model regular cab.
Ever since it’s gotten cold my battery has been draining over a period of a few days and I am un-able to start the truck.
The battery that I have is only a couple years old. When I disconnect the battery it holds its charge so I do not believe it’s the battery - although I never got it tested.
After doing some googling I tested the truck for parasitic draw but it’s only got a draw of around 0.15-0.17 amps. Even after keeping it hooked up for a few hours and overnight it’s not going above those numbers.
The alternator charges fine as well.
However I did come across something online that says if you’ve got AC power going to your battery that the diodes in the alternator are no good and should get replaced.
I checked to see if I had AC voltage going to the battery, and I had 30 volts going to it!
I replaced the alternator, checked it again and I’m still getting 30 volts AC to the battery.
What else can cause AC power going to the battery? Maybe it is this component that failed that is causing my battery to slowly drain?
Thank you so much for any ideas, because I am at a loss and ready to bring it in to the dealer.
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Joined: May 2011
Posts: 1,578
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From: Central Iowa
There’s always a given amount of measurable AC voltage. You can probe almost any 2 power and ground points on the truck and you’ll find AC voltage present. If the rectifier in the alternator was bad, you’d be seeing hundreds, if not thousands of volts; not to mention the battery would be boiling in a matter of seconds.
With a drain that small, I think the likely reason is there’s a module that isn’t powering down. When that happens, every so often it can send a message out on the data network, which then wakes up the other modules. How often it’s sending a message depends on the module and the importance of the message, but since it’s not a continuous draw, you just haven’t seen the voltage spike at the right time.
You might be able to correct it by disconnecting both battery cables and jumper them together for at least an hour - this discharges the battery backup and resets the modules.
Otherwise a shop with a capable scan tool could check for codes stored in the entire network, not just the PCM.
With a drain that small, I think the likely reason is there’s a module that isn’t powering down. When that happens, every so often it can send a message out on the data network, which then wakes up the other modules. How often it’s sending a message depends on the module and the importance of the message, but since it’s not a continuous draw, you just haven’t seen the voltage spike at the right time.
You might be able to correct it by disconnecting both battery cables and jumper them together for at least an hour - this discharges the battery backup and resets the modules.
Otherwise a shop with a capable scan tool could check for codes stored in the entire network, not just the PCM.
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