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Alternator Voltage

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7.8K views 2 replies 3 participants last post by  DJMurphy  
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#1 ·
Hello there!


i just realized that alternator voltage control loop is made by ECU. I checked my Patriot 2012 no FDII option at idle, just for curiosity and voltage loop control looks very inaccurate.

After started the engine the voltage is around 14.7V in IDLE, then i tried to increase the load by turning on internal fan, lights and heated seats, in this case voltage drop to around 14.3V/14.4V. Considering that is in IDLE, looks like normal but the strange thing happen when i remove the load. After removed the load (Lights,fan,heated seats), the voltage get a spike up to 15.0V for 2sec, then again around 14.7V.

Voltage loop control looks very slow for my opinion.

Did someone made a test like this ?

I tested voltage directly on the battery by a fluke certified.
 
#2 ·
I don't believe the voltage regulator in most cars are as instantaneous as we'd expect in other electronics. The voltage will appear to increase as load increases--voltage=electrical pressure, need to "push" additional current thru the system. I wouldn't worry about it, unless you start having unexplained problems; such as battery going dead, some electronics not working as expected, etc. But, then, that's just MY humble opinion, only constructed on electrical/electronic experience for 60 years...
 
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#3 ·
I have a Fluke 77, I get almost the same response on my '10 Patriot. 14.2-14.7 is perfectly normal. Only time I would worry if it's above 16 and below 13.5 volts continuously while the engine is running.
 
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