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Is it normal for the Alt guage to read below 14v when running the A/C ??

CASD57

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I just notice this..since I've had to use the A/c in the last week... I'm more worried that this is a precursor to a problem starting?
it stays in the white below 14v probably around 12v moves up to 14 and back to 12v slowly
 

ygmn

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My bet it is th new age computer controlled alternators and they do no try for 14 volts all the time...

Few threads in here about it.
 

BainMan

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Get the battery and alternator load tested at a parts store if you're worried or just curious. However it is normal to be below 14v, it only goes 'full-tilt' when required. The only thing that catches my attention from your post though, how long does it take to go from 12v to 14v and back? Mine doesn't fluctuate much, but might drift down over longer trips as the battery is topped off.

P.S. How old is the battery?
 

CASD57

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Not sure...I'll check the top but it looks newer, Truck is new to me Last Dec
It never really gets back to 14v for any length of time...hovers around 12-13v or whatever the mid point is in the white marking thats before and after 14v

Okay I have a tester...its says replace battery 336 CCA battery is rated at 730 CCA
 
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CASD57

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But would a weak battery cause the -14v only when the A/C is on? or do I have an Alternator and Battery problem...lol dang
 

EXT4ME

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Since you have already confirmed that you current battery is dying, I would go ahead and replace that first.

A battery, along with the alternator, will provide the power needed to run everything electrical in your vehicle.

If the battery is weak, it can not hold up it's end of the tasks and the alternator must do double duty.

That could certainly show itself as a lower than expected voltage value.

The alternator is working harder just to keep up and can not produce the full voltage is normally does.
 

CASD57

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Replaced battery.....Did it again when the fans kicked on but it recovered back to 14v plus a lot quicker and playing the radio without the truck running I used to get the warning light within minutes the "battery was low start engine" I did it for over 10 min yesterday and no warning..So I'm happy the battery was the problem....it was a 4 year old autocraft gold ..
 

CASD57

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Still doing it.....Maybe it's just normal? have not had any problems other than Alt. gauge showing below 14v at times. So I'll live with it until a real problem shows up
 

BainMan

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Can you post a video? I don't think mine fluctuates as much as you are describing, but it's hard to tell via text.

Edit: Did you get the alternator load tested? If you have a few extra minutes, just about any part store will test it for you free of charge.
 

CASD57

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Yes I'll get it load tested this weekend and try to catch it doing it on video..........This morning it went to 14v and stayed there usually in the mornings and when it's not below 14v its always above 14v... It could be I'm just more in tune to watching it now...?
 
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