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My '08 Adrenalin V8 kills batteries, no fix yet! UPDATE!

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S Silen

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My 2008 Adrenalin with 4.6 V8(80K miles)View attachment 1333 kills the battery overnight, every night. Battery is a new last week Diehard AGM, which replaced one installed Nov. 2019. Advance Auto told me it wasn't the battery but gave me a new one anyway, it lasted one day. Mechanic has replaced the alternator(new in 2018), no change. Replaced battery terminals, nope. Disabled all door locks, nope. Disconnected aftermarket stereo, nope. Something is draining the battery, it is very frustrating, I luckily have a second car but need my truck! I have started my ST about 20 times with my little lithium power pack, amazing but tiresome. Anyone have any ideas I can suggest? I love my Yellow ST and do not want to replace it.
I have a 2010 Adrenalin and had a similar issue last year. Truck just started killing batteries overnight and nobody knew where the current draw was coming from. In my case, the culprit was some corrosion on the bottom side of the main wiring harness / posts. Had a mechanic do all kinds of tests before finding the problem. Cleaned the whole area and have been good to go since. The corrosion was not evident when looking at the battery posts or cables
 

Paul Maurer 3

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Thanks S Silen from China Grove! I'll have my mechanic check that area when it gets it's next oil change. I live right on the ocean so corrosion is a constant issue- my wheels look like hell up close.
 

S Silen

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Thanks S Silen from China Grove! I'll have my mechanic check that area when it gets it's next oil change. I live right on the ocean so corrosion is a constant issue- my wheels look like hell up close.
No worries. I had one mechanic working on it off/on for a couple weeks before he sent it to this guy that fixed it as he is better with electronics. Thought the thing was possessed! When it first started, I would turn off engine and take key out and climate control lights would keep flickering with relays tripping. It was freaky. And my wheels look like hell too but I think it’s cause I got lazy about cleaning them😎
 

Richard McAlister

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In my case, the culprit was some corrosion on the bottom side of the main wiring harness / posts. Had a mechanic do all kinds of tests before finding the problem. Cleaned the whole area and have been good to go since. The corrosion was not evident when looking at the battery posts or cables
S Silen:
Not sure of the area you are talking about. Under the battery cables at the battery posts, or another area? I'd like to check the corrosion you mentioned. If you could post a picture of the area I'd be much obliged.
thanks,
rich
 

S Silen

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Since it was late winter of last year when I had the issue, let me check with the guy that found it for more clarification. He should remember since it was a unique issue
 

Richard Johns

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Bad alternator diodes may be the most likely cause. As an example, my Sport Trac has a high output alternator and if three diodes are bad, the alternator light most likely illuminate and your battery will most likely lose its charge overnight. Bad diodes allow battery drain through the altenator; in other words, the diodes are to only allow electrical flow one way - to charge the battery - not both. However, if only two or one is bad, your alternator light may not illuminate and a volt meter may also reflect it to be charging, but in fact the two or one faulty diodes will cause the battery to drain and go dead over a few days time. Repeated cycling allowing AC to enter the battery - what the diodes prevent - will kill the battery cells. I've had four batteries over the past couple years - it was illuminating discovery!
 
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