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Discussion Starter · #1 ·
Have a 2013 Nissan Ultima. Battery warning light and brake warning light are on. Charging voltage was at 15.2. I tested voltage at the battery with a voltmeter and with a an OBD2 Reader. I changed out alternator now it’s showing 15.6 V. I also have an intermediate problem with the AC head fuse blowing. I was going to look into changing out the battery voltage sensor to keep from spending another 200+ dollars I was wondering if there was a way to test the voltage sensor?
 

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There's no voltage sensor, only a current sensor (the ECM senses system voltage internally). That probably isn't your issue. If it's putting out 15.6V all the time then it sounds like the "smart" alternator driver in the IPDM or the wire connecting it to the alternator are shorted to ground. That will override self-regulation and cause the alternator to run at max output constantly. Here's your alternator layout, the Sky Blue wire on pin 4 is most likely your issue. To find out whether the problem is the wire or the IPDM, take the connectors loose at both ends and ohm it to battery + and battery -. Both should show infinity or very close to it. If not, the harness has a problem, otherwise your IPDM is probably shot. Either way, a cheap out is to sever and cap the Sky Blue wire at the alternator end. That will put the alternator on internal regulation (around 14.2V) and eliminate the dumb smartwork.

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Discussion Starter · #3 ·
I will look into that. Something else that has happened simultaneously is that the Climate control unit lost power. I found a blown fuse last week everything was fine this week is when the voltage issue started of course I did change out the alternator probably should not have and now the climate control unit lost power again.
 

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Sounds like maybe you have a wiring issue, although maybe the high voltage is causing some modules to draw higher current than they should. I'd try to get to the bottom of the voltage issue first, then chase the HVAC if normalizing the voltage doesn't cure it.
 

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Discussion Starter · #5 ·
I am trying to find the sky blue wire inside the IPDM. The one that I found is on a white connector I have unplugged it it also has a purple to dark blues pink and yellow wires on the plug. Am I dealing with the right connector?
 

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Discussion Starter · #6 ·
If that’s the right connector the sky blue wire inside ID p.m. connector is reading 38.4 ohms to negative and direct short to positive. The sky blue wire on the alternator and is reading 46.35 to negative and open to positive.
 

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Discussion Starter · #8 ·
I cut the sky blue wire on the connector at the alternator and capped both hands. Restarted vehicle and charge is at 15.9 V. Took volt reading out the battery
 

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Discussion Starter · #9 ·
With the clarification of which plug is the correct one. I was actually not in the IPDM. I was in the box in front of IPDM. But after removing the connector that you’ve identified on the sky blue wire both ends are showing opened but I have the sky blue wire cut in half and taped back at the alternator voltage is remaining 5.9 V
 

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Discussion Starter · #10 ·
When I remove the entire plug off the alternator voltage goes to 13.7 V in the battery and brake light go off. With the plug connected at the alternator and the light blue wire severed voltage is 15.9 and the battery warning light and the brake light come on
 

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Hate to say it, but that's sounding like a bad alternator from the parts store. Disconnecting completely kills the field coils, so of course the charge will drop way off. If severing the control wire didn't drop the charge rate then the alternator itself has to be at fault.
 

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Discussion Starter · #12 ·
I’ve got another alternator coming Wednesday of next week. It has been a head scratcher. Thank you if that doesn’t fix it I may reach back out. Happy Thanksgiving! May the Lord bless you.
 

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Discussion Starter · #13 ·
Also I forgot to mention with the alternator that’s in there now and the sky blue wire cut loose after turning the car off I noticed there was a humming/ whining noise which appears coming from the alternator, when I disconnected the charge wire, meaning the wire going to the battery the humming stopped. It’s almost like it was trying to discharge or something like that.
 

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Also I forgot to mention with the alternator that’s in there now and the sky blue wire cut loose after turning the car off I noticed there was a humming/ whining noise which appears coming from the alternator, when I disconnected the charge wire, meaning the wire going to the battery the humming stopped. It’s almost like it was trying to discharge or something like that.
That definitely "ain't right".
 
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