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Discussion Starter · #1 · (Edited)
What does your truck read. I was performing some test and took a voltage reading at my battery terminals at idle. 13.0 to 13.2 volts. IMO this is low. Might have been the first time I have ever checked. What do your trucks read? Alternator going south? Do our alts have a voltage regulator that wears?

I wanted to see what the voltage was at higher engine speeds, but realized that I can not increase the throttle from the engine. Throttle by wire. ANyone know of a way to do this easily from the engine bay?
 

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Mine reads 12.6/12.7 at idle goes up to 14 and change under load
 

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ANyone know of a way to do this easily from the engine bay?
** shouting around side of hood **

"Ok Honey, press on the gas pedal now for about 3 seconds"

Sorry couldn't resist :) I am not sure that there is (at least an easy way) to do this but I'd also like to know if there is.
 
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Mine reads same as GMK14. I obtained the voltage readings using a bluetooth OBD scanner and a phone.

It's like it kicks on a while to charge a little, then kicks off when the charge is ok. I figure its a fuel saving feature.
 

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On these trucks, it can vary A LOT with temperature and battery state of charge.

On a cold start, mine is in the high 14's. After the battery is completely recharged and the engine is warmed up, it's down around 13.1 or 13.2.
 

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I wanted to see what the voltage was at higher engine speeds, but realized that I can not increase the throttle from the engine. Throttle by wire. ANyone know of a way to do this easily from the engine bay?
Maybe try something like an adjustable rod or a stick that you wedge between the accelerator and the seat. Probably could work it out so you can keep the truck at a certain rpm while you have a look. Oh and put the truck in neutral to...
 

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Discussion Starter · #7 ·
On most vehicles I have ever worked on the battery reads 14+ volts at idle. If not something is wrong. Interseting that we see such variation. I took a reading both right at start up and after things reach operating temp.

I would has asked the wife or kids to help depress the gas but I was home alone. There is this tool I know of to depress the gas pedal. SMOG techs use it to set a particular RPM. But I guess gone are the days of grabbing the throttle body butterflies and giving them a twist.


It is a shame that the the voltage meter on our dash is simply a dummy display. It would have been helpful if that thing really read the voltage. And what is even more stupid is the scale. The only numbers are 8 and 18. What about the more useful range like from 11 to 15. I guess its purpose is if the needle is anywhere in the cebnter range the car is charging.


I think that I am going to get a little plug in voltmeter to monitor things
 

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Discussion Starter · #9 ·
On a serious note this time :) Have you tried this diagnostic feature in the link below? One of the data items is volts, and you can see it in one of my pictures.

Found a secret diagnostic screen on my second gen Frontier... - Page 2 - Nissan Frontier Forum
Interesting. I just did this test. Upon start up it red 14.1-14.2v. So I went and grabbed a volt meter and probed the battery. 13.2 like yesterday. Jump back in the cab and look at the test reading. 13.1-13.2. Guess the truck bumps down the voltage if it the battery doesn't need charging. Maybe I will leave it in test mode and see if I can monitor the battery voltage on my drive home.

Thanks for the insight.
 

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Fyi I monitored on a long drive and noticed it was 13.1V +-.1 or 14.1V +-.1.

A 1V jump up when needed and an 1V back down after a while, nothing in between and the jump up or down was immediate (not gradual).
 

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Mine is usually 14.1 after startup and decreases to 13.1 over about a minute.

I understand it has something to do with the current sensor over riding the
regulator to make the truck more fuel efficient. I've been wanting to test it by
unplugging it under various conditions to see what effect it has, but... haven't
gotten around to it yet.
 

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I feel like I have an issue with my alternator. For the last 4 years or so my truck eats batteries at the rate of one a year. I have my Ham radio hooked directly to the battery. It has a voltage meter that registers the voltage when turned on. It sits at 13.0 to 13.1 after the truck has warmed up. I even checked it while driving and there it stays.

On this last Thursday I had an issue with starting it again. I finally got a charger/maintainer. it can charge up to 15 amps. I charged it partially and that evening charged it again. After 6 hours it still hadn't gone into maintain mode. It was by morning.
 

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What does it matter if the topic is still relevant?
 

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Maybe try something like an adjustable rod or a stick that you wedge between the accelerator and the seat. Probably could work it out so you can keep the truck at a certain rpm while you have a look. Oh and put the truck in neutral to...
Or just hook up your volt meter and put it in a place you can see from sitting inside the cab
 

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After observing for the last week I am sure it is my alternator. At startup it is always the same, but after a few minutes it may go down to 12.8 and stay there or go up to 13.8-14.0 and just stay there. I've seen it stay at 13.8, then stop at a stop-n-rob and when I start it again it might down to 13.0 and stay there. It isn't consistent at all.
 

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After observing for the last week I am sure it is my alternator. At startup it is always the same, but after a few minutes it may go down to 12.8 and stay there or go up to 13.8-14.0 and just stay there. I've seen it stay at 13.8, then stop at a stop-n-rob and when I start it again it might down to 13.0 and stay there. It isn't consistent at all.
Mine is about like what you describe...and is a '15 w/ 36k. It is my understanding that these changes are normal and to be expected. Keep us posted if you have your charging system checked. This can easily be performed at several kinds of shops. In the past, I've used a local Mom&Pop battery shop for tasks like this.
 

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Here's a quick way of bypassing the "Variable Voltage Control System" - Restores full control of battery charging to the voltage regulator inside the alternator (eliminates voltage reduction from the ECM) - Increases typical battery voltage from 13.1-13.2 volts to 13.6-14.1 volts:

VVCS Defeat

The yellow wire is the "Power Generation Command" signal from the ECM to the alternator voltage regulator. After cutting it, the voltage regulator operates on its own.
 
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Here's a quick way of bypassing the "Variable Voltage Control System" - Restores full control of battery charging to the voltage regulator inside the alternator (eliminates voltage reduction from the ECM) - Increases typical battery voltage from 13.1-13.2 volts to 13.9-14.1 volts:

VVCS Defeat

The yellow wire is the "Power Generation Command" signal from the ECM to the alternator voltage regulator. After cutting it, the voltage regulator operates on its own.
Where did you find this? This is what i've been looking for. That variable voltage nonsense is a pain.
 
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