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Repair guides and support for internal and external vehicle accessories including: chargers, luggage racks, aftermarket modifications, air conditioning and heating units.

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Toyota Highlander charging system acting strange

I put a voltmeter on a 2017 Highlander that I just bought. The readings don’t make any sense.

When it is idling in park, the voltage is 14.6V.
If I am idling in Drive, it is 12.4V. RPM ~ 700. If I give it a little gas to bring the RPMs back to 1000 it does not change back to 14.6V where it was in park.
When I am driving, the voltage is 12.4V. RPM can be anything.
If I take my foot off the gas pedal while I am driving, it goes back to 14.6V.
That can't be right.

I expect it to be in the 14V range while driving and possibly to decrease if the RPMs fell as in when I took my foot off the gas.

I have checked the belt and it is in good condition and tight. There is no noise that would indicate it is slipping.

Can anyone explain this to me, or is there a problem I can’t explain.

Answer this question I have this problem too

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the answer is fuel economy.

When the engine is driving the vehicle, the alternator is cut out to allow all the power to go to the wheels.

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When the regulator gets a call to charge your volts climb. Seems like it’s acting normal to me.

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Why would it get a call to charge only when I take my foot off the gas?

Why is it showing 12.4V, which is not a full charge voltage, while it is running at a higher RPM?

It does not make sense to me.

If the battery voltage is at 12.4V then it should be charging.

And my voltmeter is reading about 0.5V high.

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Clean battery connection

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Not relevant.

1. Battery was defective and replaced in warranty.

2. operation is by design to increase mileage rating. It is much harder on flooded batteries than EFBs and AGMs. The flooded battery was installed b4 I bought it.

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bill will be eternally grateful.
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