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2010 Tundra Crewmax 5.7
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I have a 2010 Tundra Crewmax Limited 5.7 with tow package

I've been dealing with a charging system issue for 5 months now.

It will stop charging while driving. The battery light does NOT turn on when this happens.
Voltmeter just drops to about 12V and declines as the battery slowly goes dead.
If you turn off the truck while it's not charging and then turn the key to the run position the battery light does NOT turn on.

If the truck is cold and you turn the key to the run position the battery light DOES turn on.

Sometimes while driving the volt gauge will jump up and down from battery level to charge level. Occasionally the battery light will flicker while this happens.

I have replaced the alternator ( that's a nightmare). Did not improve the situation.
I had the replacement alternator tested before installing.

I have also replaced the following fuses : ALT-S, MET-B, MET, LH-IG. Did not improve the situation.

I've also swapped batteries. Again did not help.

It seems like the clue is the battery light NOT turning on.

As the weather has turned colder it takes a lot longer for charging to stop. Some trips it does not act up at all.

So it seems to be temperature related and is probably in the engine compartment and not in the cabin?

Anybody have any ideas?
I've run out of things to try.
 

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Could potentially be a wiring issue, either the charge line or a ground. If the alternator is charging properly, but not reaching the battery then you need to figure where the charge is disappearing. If you can verify that the charge line is delivering the charge to the battery then make sure the ground cable for the battery is secure and not corroded.
 

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05 camry 07 tacoma
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A voltage drop in the charging circuit either between the alt pos and bat pos post or bat neg post and the alt case(neg) can cause problems.
There should be no more then a few tenth of a volt.
When not charging measure for voltage drop in the charging circuit to help isolate problem.
 

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Sounds to like you have a 'Intermittent' bad connection. I'd put a volt meter on the battery output terminal of the alternator. All the lights on, A/C on, load the battery with everything you can, then do what's called a 'wiggle test'. Wiggle all the wiring looms between the alternator and the battery and the ignition. Also check the connectors for corrosion or bad connectors. You may need to get a wiring schematic and run down the alternator exciter circuit to find your problem. Good luck :)
 
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