Truck won't run w/o battery... Alternator or voltage regulator bad? - Toyota Nation Forum : Toyota Car and Truck Forums
Tundra 2nd Generation (2007-2013) Discussion of the 2nd generation of the Toyota Tundra

 
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post #1 of 6 Old 11-21-2018, 09:14 PM Thread Starter
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Truck won't run w/o battery... Alternator or voltage regulator bad?

My battery won't charge. I'm heading to get it tested/replaced, but this is the second battery in 2 years that dies and won't recharge. I'm pretty sure it's my charging circuit, but don't know how to tell whether it's the alternator or the voltage regulator (or are they both in the same unit?).

When the battery is DEAD, I can use my jump pack to get the engine started. But if I take the jump pack off in the first minute or so, the engine stalls out. After a minute, it keeps running, but the volt meter I have in the power outlet is jumping from 13 to 14.5, and all the lights are flickering. Perhaps that's normal? Or should the alternator be sufficient to drive all the (mostly stock) electronics w/o a battery?

This is an '07 5.7l limited.

FWIW, I have a cheap Walmart Hammacher-Schlemmer charger with an electronic display. It refuses to charge the battery when it's in the 'dead' state (2 volts). I have to start the truck, let it run for about 10 min, then the battery will have about 10V. Then the charger will work, but eventually the charger blinks 'error/check battery'. Which is what is causing my doubts about the battery health.
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post #2 of 6 Old 11-21-2018, 11:22 PM
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Are you trying to run your truck with no battery connected? That's a good way to kill your alternator and the electronics in your truck. The alternator has the regulator circuit built in, however the alternator is partially controlled by the engine computer.

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post #3 of 6 Old 11-21-2018, 11:34 PM Thread Starter
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Originally Posted by 71Corolla View Post
Are you trying to run your truck with no battery connected? That's a good way to kill your alternator and the electronics in your truck. The alternator has the regulator circuit built in, however the alternator is partially controlled by the engine computer.
No, battery has always been connected. When I remove the jump pack (leaving only the dead truck battery connected) it dies if I don't give it at least a minute of run time
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post #4 of 6 Old 11-21-2018, 11:52 PM
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Originally Posted by erkme73 View Post
No, battery has always been connected.
Oh okay good. If possible get both the battery and alternator bench tested is the alternator difficult to remove?

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post #5 of 6 Old 11-23-2018, 05:05 PM Thread Starter
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Originally Posted by 71Corolla View Post
Oh okay good. If possible get both the battery and alternator bench tested is the alternator difficult to remove?
I don't really know. I haven't been able to pull away long enough to really start looking at options. My main concern was if the alternator and VR were two different item. But, if they are, as you say, all inside the alternator, then the decision is pretty simple - I'll just order a new one from Rock Auto (<$200) and swap it out. The truck is now 11 years old and has nearly 150k miles, so if that's the worst of it, I've nothing to complain about.

The flickering lights and stalling out only happen if the battery is dead (i.e. 2 volts). I don't know if a properly functioning charging system is supposed to be flicker-free, or if that's just what happens if the battery isn't providing enough static voltage to act as a capacitor.
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post #6 of 6 Old 11-26-2018, 06:01 AM
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Quote:
Originally Posted by erkme73 View Post
My battery won't charge. I'm heading to get it tested/replaced, but this is the second battery in 2 years that dies and won't recharge. I'm pretty sure it's my charging circuit, but don't know how to tell whether it's the alternator or the voltage regulator (or are they both in the same unit?).

When the battery is DEAD, I can use my jump pack to get the engine started. But if I take the jump pack off in the first minute or so, the engine stalls out. After a minute, it keeps running, but the volt meter I have in the power outlet is jumping from 13 to 14.5, and all the lights are flickering. Perhaps that's normal? Or should the alternator be sufficient to drive all the (mostly stock) electronics w/o a battery?

This is an '07 5.7l limited.

FWIW, I have a cheap Walmart Hammacher-Schlemmer charger with an electronic display. It refuses to charge the battery when it's in the 'dead' state (2 volts). I have to start the truck, let it run for about 10 min, then the battery will have about 10V. Then the charger will work, but eventually the charger blinks 'error/check battery'. Which is what is causing my doubts about the battery health.
External regulators have not been used for decades. Get a good battery and check charging voltage at the battery with a mutitmeter. It would be good if you could check charging amperage also, but that requires an amp clamp. If your alternator is covered in oil it is most likely bad. If you don't really have the stuff or, know how to check the charging system, it is usually about 1/2 hour of labor at a shop.
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