The Nissan Path

So I'm getting ready to go on vacation and the girl is out of town with her sister; I go out to grab some chow and on the way back I notice my battery and "BRAKE" lights are lit. Meh, no big deal right? I pull over to the side and give her the ole' reboot. Brake light and Batt Lights remain on... So I set my BullyDog GT to display the voltage information, sure enough the instant feedback is showing a fluctuating 12.0-12.6v and dropping. I get into my driveway and we are in the high 11s I go to give it gas, the engine won't even rev... I shut it down, wait a few min, start it back up and up the steep gravel hill\driveway I go.

I take the Pathy to Advance and have them test the battery (2 yo Optima Yellow Top). I'm told the battery is fine, but the Alternator isn't pumping out anything. So without any hesitation I order a new alternator, head out to the beach with the Pup and Girl and give UPS a week to do their thing.

I return from vaco and a nice Shiny bench tested Alternator is waiting on my doorstep. Fast forward a wheel well cover here, some scraped knuckles there, and new shiny alternator is installed. 14.4v on the BD GT and a breath sigh of relief (too soon).

I go to take it for a drive, within 5 miles the voltage has dropped to 13.3V by 10 miles 12.7-12.9V but no less. After a healthy torrent of obscenities it was back to research mode.

Starting to think the "BIG 3 upgrade" might alleviate my issues. I decided to break down my terminals, wire brush and contact clean them. Not wanting to run into further connectivity issues I coated every surface (pigtails, nuts, bolts, washers) in dielectric grease and snugged them down. I decided since I didn't want to take off the front pass wheel and well cover (needed to gain access to the atl) I would simply reground the neg terminal to the engine and that might yield a change. No Dice.

So I went digging again and found a similar issue going on an AU pathfinder site that seemed to affect the 2.5 oil burners. Their solution was cutting one of the wires (Green if memory serves) on the Alt pigtail and they received a constant voltage at all times. Now I'm no butcher, I didn't do the rad bypass, I'm not clipping any wires on my alt. but with a little more digging I uncovered this was due to some issue with the variable voltage sensor. So until the system determines that the battery has dropped below a certain voltage threshold it will not charge the battery... Even stranger, there is a sensor (located near the battery tray which all the grounds should go through for proper metering. Although I did resurface the connections on that "sensor" the engine ground was too hard to reach, so I chose another point and directly connected it to the neg term of the battery. So I will try to move the connection from the neg terminal to said sensor hoping that this is a byproduct of a bad ground.



Any folks out there with Bully Dog GTs, go for a drive after about 10 miles look at your voltage. Are you at a steady 14.4 the entire time or do your numbers fluctuate.

Mind you when the Pathy starts up it is at 14.4-14.3v and only after 10 miles does the voltage hang out in the upper 12s. If I crank up my stereo, turn on the AC and put on the heated seats there is no change or dip...


My questions for any Techs out there:
What components in the VVS might be cause these symptoms?
Is there a way to configure the voltage threshold?

The voltage sensor is part of the negative battery cable. It measures the residual voltage going back to the battery, thus it's important if you are adding any electrical components to your vehicle (i.e. additional external lighting) that you do not ground directly to the negative battery post terminal, but to a body ground or a point behind the voltage regulator. The reason for this is the alternator is computer controlled and if the alternator only works as needed, it creates less engine load and results in better gas mileage.
Charging system voltage should measure between 13.2-15.0 volts when running, at idle and at 3000 RPM, with loads "on" as well as with loads "off." Most Nissans usually charge about 14.7 volts, in my experience. I've also found in my experience, that most aftermarket alternators have a history of being unreliable, especially in Asian makes like Nissan, Toyota, etc. Advance Auto Parts is good for some things, but I don't use them for electrical parts like starters, alternators, ignition modules, etc. When it comes to those parts, one is better off spending the money on a genuine Nissan part. They may be more money, but who wants to keep replacing an alternator or starter several more times? At the very least, if you have to go aftermarket, go with a part from the OEM Nissan manufacturer, like Hitachi or Mitsubishi.
It's possible you could have a bad voltage sensor, but far more likely you have a faulty regulator. Only way to find out would be to try another alternator or go through the testing procedure in the factory service manual, which will likely require a scantool.

Fofiddy wrote:....Their solution was cutting one of the wires (Green if memory serves)......

Ahh yes, the green wire mod. Everything I've seen regarding this and computer controlled alternators applies only to 2010 and on models though.

Fofiddy wrote:....Mind you when the Pathy starts up it is at 14.4-14.3v and only after 10 miles does the voltage hang out in the upper 12s. If I crank up my stereo, turn on the AC and put on the heated seats there is no change or dip....

That bit right there seems to go against what I've read on the charging issue. At-least when they system is functioning normally the V should rise when turning headlights, and other factory electronics on. Could just re-look at that mod, check the harness plug for that wire then de-pin it from the plug real quick as a test. No harm no foul that way as you can slide it right back in.

Thanks for your input guys!

@Blink- Wasn't aware it was limited to 2010-12. From the chatter I assumed it could have been the difference between the Spanish and Asian builds (as that seemed to be another factor in that thread.)

@SMJ- I had a feeling I needed to reground to that sensor... I believe the OEM is a Hitachi Alt. The rebuilt unit was nice and shiny but that is no way to measure performance. BUT, If I'm going to spend OEM replacement money for an Alt (and taking off the pass wheel and removing all that stuff again) given my additional stereo equipment (just a 900watt 5 channel amp recently upgraded and heated seats I installed back in 05 and toying with the possibility of aux lighting) if I may be better served by 200amp alt?
https://ruggedrocksoffroad.com/nissan-p ... 35961.html


OK so here is where I interpreted the Ground VVS terminal was:

I know it looks crappy but that's what happens when you drive an un-garaged truck in New England for 10 years.

I relocated it Wednesday and noticed an immediate .3 V improvement when driving around the next 2 commutes, last night and this morning my voltage stayed in the high 13's to the 14.1 volt area. So yes, an improvement and enough to convince me to upgrade my body ground to the same terminal in the near future...

Honestly I'd be a lot more upset if the truck was failing or under performing, I'm more intrigued right now...

Nissan alternators are made by Hitachi. As far as the "Mean Green" alternator, it sounds good, but I don't have any experience with them to give an opinion one way or the other.