Alternator output voltage?

#1
Installing a winch, so figured I'd test my battery and alternator.

Battery is reading 12.6v when the truck is off, which I think is perfect
When the engine is running (at idle) I'm reading 13.99v - I thought a healthy alternator should be between 14.2 and 14.5v? Does the mean the alternator is starting to go?

This is on a gen1 (2004). I know some cars have variable output alternators, does the 1st gen Xterra?
 

DiploStrat

Expedition Leader
#3
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When the engine is running (at idle) I'm reading 13.99v - I thought a healthy alternator should be between 14.2 and 14.5v? Does the mean the alternator is starting to go?​
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Probably means that your alternator is perfect. The voltage is, however, not high enough for a large, deep cycle battery. You will need to raise the voltage to about 14.4v (at 20C), use a B2B (battery to battery charger) or look into lithium batteries for your camper battery. This latter option might be well worth it as you don't have a lot of space or weight to play with.

This subject is beaten to death on the 12v forum.
 
#4
Anyone else with a 1st gen test their voltage while at idle? Curious if other folks are getting anything higher around 14.4v?

Screen Shot 2018-07-09 at 12.18.56 PM.png

Looking at the FSM for my truck, 'Regulated output voltage' (which I think is what I'm testing?) is 14.1-14.7v - so I guess I'm under spec?
 
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#5
I have an 03 frontier and at idle with no accessories on im only at like 13.8-13.9v. That is measuring through the Nissan data scan obdII app on my phone. Going down the highway with lights and ac on full blast it honestly drops to 13.6-13.7. Battery always good at 12.6 or so with the engine off. Ive been looking at switching to the Quest alternator for more amperage.
 
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