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Battery voltage jumps up and down..


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Four months ago placed new Battery and noticed 11,6v while driving on the voltmeter and had also flickering lights at idle sometimes.
Solved that with tightening up the Battery clamps and never seen in again.

Now my Battery voltage is very fluctuating while driving. I can monitor that on a USB outlet with voltmeter.

While driving its 12,2 or close around that. While accelerating also 12,2.
But.. when i take my foot off the pedal it goes upto 14,1-14,4v. Every time again i see it jump up and down.
To make it even more strange, at idle it shows 12,2v in every gear but when i shift to P its suddenly 14v.

Is something wrong with alternator or maybe it is the voltage sensor like in ´flickering lights´ topic ? How to check?



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Problem solved. There is no problem. 😀

My 2012 is a Euro5 emission standard and is equipped with a ´smart alternator´. To reduce emission and power consumption it is normal to see 12,2v while driving and normal 14v charge voltage when coasting.

Early IQs are Euro4 emission standard and some can have a normal alternator.

Hope this info can help others in the future.. 


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Hi Dutchrav, 

I too have seen this. It got me alarmed when we were sitting in traffic and I see the little cigarette lighter insert drop from 14V to 12V2, and I get on the phone to find the number for the AA in preparation for what I was expecting to be a roadside recovery. 

When we got home safely, I wondered what on earth was going on. Low and behold, I find that the charging system has some intelligence built into it, and the alternator no longer simply dumps 14V at the Battery terminals 24/7. 

This got me going too, but I am glad we found our answers 😉 makes Battery or charging system fault diagnosis that much more interesting when something is going wrong!

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Right, i almost ordered a new alternator!

When in doubt, unplug de 4-wire plug on the sensor that is mounted on the - pole of the Battery. Disconnected there should be around 14v with engine on anytime.

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